There is several of factors you should consider:
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Does it have a healthy amount of users: between 1k-10k users are probably the sweet spot right now. You don't want too many users because it will cause performance problems. And instances with too few users has too many unknowns.
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read the rules see if you agree: servers can have wildy different rules ranging from no NSFW to no downvotes. If they don't have any rules that is a red flag too. You want an active moderation so the instance doesn't get run over by bots.
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Does it look low effort: check the banner, how the announcement formatted.
That is probably all the basics
If you are new you probably want to decide which game engine you want to use first, then learn one of the languages that engine supports.
Most popular choices would be: Unreal engine, Unity and Godot. Hovewer if your goal is to get into game dev industry by far the most popular language would be C++ followed by C#.
Depending on the scope of your game(if it is a very simple 2d game like 2048) you might want to consider Python too. it is known for being one of the easiest languages to learn and you will have easy time researching the points you get stuck on.