A generalized question can only get a generalized answer.

The most significant accomplishment is validating that the product you have built is a fit with your target market. This is demonstrated primarily by engagement (the people who sign-up or who previously visited, continue to return) and secondarily by growth, ideally based on word-of-mouth or viral growth but effectively converting paid traffic is a great second prize.

Other significant accomplishments include:
Not running out of money
Recruiting and retaining great talent who believe in the founders' vision.
Your loved ones not thinking you're as crazy as they thought you were a year ago.

I'm happy to talk to you in a call to give you more specifics about what you want to set as your goals more specific to your startup.

The first year for me is the year to prototype as much as possible. Do the MVP (minimum viable product) with quality and track down analytics to the user engagement.
Start with the core idea and build out worth. The less features the better. Make the essential and remove all non essencial features.
The goal for the first year is to prove that there is a market/need for your idea. If it doesn't grow on it's own, then probably you need to tweak it and adjust your initial idea.
Users should bring users. Users should come back. If that doesn't happen, then probably you are working on something that can make all the logic in the world but that users don't want or need.
In a nut shell, the first year is trial and error. Analytics, tune up, change, try again, until you reach a consistent growth.

Hi!

My name is Mijael Feldman, im co-founder of BOMBAcamp (www.bombacamp.com), an early stage startup accelerator for spanish speaking market.

How many paying customers you have for your product/service.
Visits/users/suscribers/followers are worth nothing if you dont have people paying for you product.

Best validation for a startup in its first year is to habe customer paying.

Validate a problem -> validate the solution
-> test solution -> paying customers. Dont worry about getting a million customers, focus on getting the first 10, then 100 then 1000.

Hope it helps! If you want more details of how doing this process i am open to jave a call with you.

First year for a start-up is basically about surviving the storm. It begins with the plan and the implementation of the plan. Once you have established the idea, it is time to assess whether there’s a big enough pool of prospective buyers. By now, you have successfully verified that your idea has that “success” potential. Feels good, right? Well, brace yourself – it is time to test whether people will actually spend money on your product. In other words, is it truly commercially viable? This step is critical. A lot of your ideas will seem great in theory, but you will never know if they are going to work until you test your target market’s willingness to pay.
Before key accomplishments there will be lessons that you can learn from the struggles and the challenges of first year. Let us look at the accomplishments one by one.
1. Stress challenges personal relationships: Launching a business, assessing market opportunities, aligning the right team and figuring out how to execute properly is challenging enough; add the fear of the unknown and financial insecurity, and you have a recipe for a heap of stress. While many people can handle this on their own, when these stressors are not thoughtfully communicated with the people in your life that you care most about, another level of stress can overshadow your ventures and adversely impact your performance. No matter how busy you may become trying to fulfil your dreams, always make time for your spouse, your children, your family, and your friends. Your support system will be with you through thick and thin, which, any entrepreneur knows, can happen at any time. When assessing your accomplishments, you should understand that they don't need to be life-changing events to be valuable. For example, think back to your first client or customer, or even back to the last time someone hired you. They chose you. They believe in you. They trust you. It is easy to find yourself down when you lose a client or a deal, have a bad quarter, or miss one of your goals. But you can reassess, recalling what you have been able to accomplish and overcome, to positively impact your personal perspective and your business, too. Overcoming self-doubt will help you power through the rocky times as a business owner and help you reach your first-year marker and to go beyond.
2. You will want to get a job and hate yourself for it: When every entrepreneur says that you are going to have your ups and downs, they are right. The challenge for most entrepreneurs is recognizing when they have reached a peak or whether they are in a valley. When you're down on your luck, scraping by financially, overly stressed, suffering from depression and self-doubt or any one of the other screaming signs that you have fallen to a low point it's very tempting to run for the hills and go back to working full time. It is not what you want. The truth is, you never know what is going to happen and you would likely be capable of living on less money than you think.
Are there no milestones to accomplish only lessons to learn? Of course not. There are milestones you can achieve.
1. Establish a Strong Business Model: Creating a business model requires time, focus and the development of smart strategies to spend money wisely. Your business model may adapt over time, but it is the first and most important milestone to reach when planning for success. A business model is not just about the business plan but about mapping out how you will create ongoing value for your customers too. The key is to firstly identify your specific target audience, what your customers’ value and how your product or service will deliver that value to them. Along with establishing a business model, determining your finances and how your business will generate revenue is critical. Consider carefully what your cost structure and profit margin will be. If you find that your expansion plans require some extra help, a small business loan can provide the initial boost to get things rolling and set you up for even bigger growth.
2. Achieve Customer Loyalty: To truly achieve success, your business will need to maintain customer loyalty; and this milestone will be one of the most rewarding. Landing your first repeat customer will not only be great for business, but also give you confidence and excitement for more repeat business. So, how can you achieve customer loyalty? Excellent products or services at reasonable prices are naturally desirable, but they are typically secondary to customer service in this case. Building relationships with customers is vital to the growth and stability of your business and this will require dedication and an understanding of your customers’ needs to provide them with real solutions.
3. Developing a Marketing Strategy: Brand recognition and reputation will be crucial to your accomplishments, so your marketing strategy should be a top priority in your first year. Smart marketing can actively bring in new business and engage with new customers, so it is important that you market specifically to your target demographics. Remember that your marketing plan needs to be reviewed and revised at regular intervals to keep it relevant. Make sure to consider your budget when developing your marketing strategy. The most common marketing mistakes made by businesses involve money and spending enough on generating further leads. Some business owners outsource marketing, others choose to create and carry out all the marketing themselves; regardless of the choice, as much time should be spent on marketing the business as is spent on the business itself.
4. Time to Staff Up: By keeping a close eye on your outgoings and incomings you’ll know when you’ll be able to handle any extra costs such as employee salaries, to maintain the demand for your products or services. Employing additional staff is a great turning point towards realising your business growth. But before you build your team, ensure you take time to plan an effective employee training programme. Ensure your new team members have a good understanding of running the business and your future vision. If everyone is aware of the collective mission, it will empower everyone in their work and lead to a greater motivation to achieve results.
5. Reach a Number of Sales: If you have reached all the above milestones by developing a profitable business model, customer loyalty, brand awareness and a great team you should be on your way for continuing success. And the final business milestone will be to reach a significant number of sales. As part of your business model to generate revenue and make a profit, you will ultimately aim to reach that goal as planned.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath