The question isnt easy to answer as you dont need an instance to participate. It is far better if you join an instance and spare yourself the hassle of admin and/or mod work. If you absoluteky want to have a community which you can build and mod, you can do that on any instance. If you think you can provide something that nobody else can then you could open an instance. But in that case i suggest finding people to do this with because it is a large project.

And only after all those considerations, you should think of the tech aspect. You can get a vps for 10 bucks a month and host lemmy on it, probably amongst other things. But i would probably not do it if youre not really curious about server hosting stuff. Managed hosting (which is the offer you mentioned) is another idea but it isnt worth it imo. Rarely will someone really have the need to use that and then the company provoding needs to make money so you will lose.