I believe that expertise comes with time, and a lot continuous effort. Of course, all that other people will answer here is a solid complement based on each other experience.

Some good tips are, study and practice all learning paths available on official mendix academy.

Try creating new features and services of any idea or type you can imagine or argue with friends.

Never stop learning, knowledge is never enough.

Keep in mind that the path is long, and try to have fun in the meantime. Don’t forget to drink water.

As I'm currently also trying to make my way to expert (slowly but surely), here's some things I've found helpful:

• Check out the requirements for becoming an expert (scroll down all the way)
• Follow as many learning paths as possible, but not all at once. Try to put things into practice as you learn them before moving on to the next thing. Everything makes so much more sense when you've tried them out in actual projects (preferably for a client)
• While you do projects, keep your portfolio up to date. This will save you a lot of time in the end as all your experiences on the relevant projects are still fresh in memory.
• Make sure you get enough experience as a lead developer. As per the prerequisites, just being a good developer on a project isn't good enough, you need lead dev experience.
• Part of the requirements is getting enough points on the Mendix platform. This can be pretty tricky, especially if you don't use Sprintr for things like feedback / stories, so look at the Points List (section 7.1 through 7.6) to find ways to up  your score. Participating in forum discussions is a good way to earn points, and it's also very educational.
• Participate in Mendix Meetups. Many of them have interesting topics that will help you become a more knowledgeable Mendix developer.
• Make sure all your work is peer reviewed, and that you are the one to fix whatever the other person found during their peer review. It really helps you learn from your own mistakes. Also peer review others’ work – it will help you recognize neat tricks that other developers use to implement things in a smart way.

Those are the ones I can think of off the top of my head. There's probably more though!

I believe that the first thing is to complete the learning paths, since you’ve completed the academy, you’ll have enough knowledge to explore everything in mendix and to implement solutions for your problems.

Good afternoon, as other colleagues mentioned the learning path is the best roadmap for you to acquire the necessary knowledge of the Mendix platform both for certification and to build your career as a developer. The learning path has a complete, objective content and a logical sequence that facilitates learning. Another tip would be to look elsewhere like mendix community on youtube that also add a lot of value to learning. Good luck on your journey!Good afternoon, as other colleagues mentioned the learning path is the best roadmap for you to acquire the necessary knowledge of the Mendix platform both for certification and to build your career as a developer. The learning path has a complete, objective content and a logical sequence that facilitates learning. Another tip would be to look elsewhere like mendix community on youtube that also add a lot of value to learning. Good luck on your journey!

Follow the academy lessons and just start building. Try things out for yourself. It helps to have an idear or a challenge for yourself. Having multiple projects helps because you are more likely to touch everything within the Mendix modeler.

Regards,

Ronald

https://www.youtube.com/channel/UCybYiRhBPsLRcHeaqqsnovQ