I have never personally encountered a proboards forum that survived more than a few months; the restrictions and issues with forum-as-a-service companies are just never worth it.
On the technical side, its not hard to host a forum yourself. You can do it on any budget web host that provides PHP, and it should not be more than
6 euro a month; and if the forum grows, its easy to move a self hosted forum onto more powerful hosting - if its done well, your members wont even notice.
There are many popular forums that have been run for years by people with minimal-to-no code experience; however having PHP experience and being able to dive into the code and make edits is a HUGE asset for any forum admin. I've gotten quite a few emails from people who have visited this forum, then tried to replicate it themselves without having the skills, and have had to go away disappointed because it's just not possible to do that. However for a basic forum without any custom features, it's not hard at all, anyone with basic web skills can handle that - so temper your expectations to your skill level, and ask yourself how willing/interested are you in learning to mess with the code.

I recommend picking any popular PHP based forum (
SimpleMachines,
phpBB,
MyBB etc), you should try out a few, install them, see how they feel to you (try making test posts, messing with settings, installing mods etc), visit their community help boards and see if the community is good, have a look at their mods/themes and see if they offer the kind of features you want. I don't recommenced using more complex forums like Discourse, or "premium" ones like XenForo, they are costly to run and not much fun to customize. Think about what you value? For example; Do you want a modern feeling forum that may not support old themes (myBB might suit you), or would you prefer using old themes even if it means the forum software is clunky? (phpBB might suit you)
Keep an eye on the state of the development community, you want one that's up-to-date and active; for example, Vanilla Forum was one of my fav forum softwares, but they sold out, and the code will not be getting updated any more; whereas I've had arguments with the Simple Machines team, but they are very dedicated and there are some great people behind it. It's fine to use outdated software if you have the skills to patch it yourself, but if you don't, you neeeeddd to make sure its gonna be updated by its dev team not just now, but 5 years from now.

Finally, it's common in forum culture for developers to offer paid mods or plugins for forums; this is normal and often the best mods are paid; you should decide if you have a budget for that, and set a limit to your budget, only buy mods if you really need them, and research the developer your buying from to make sure they have a history with that forum software community, and to make sure they are not a jerk who wont help you if there are issues!
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A few very important questions to ask yourself, why are you making a forum (whats it's subject/goal?), and, why are YOU making a forum (what do you personally have to offer people who join?). How are people gonna find your forum (where will it be shared and linked?), and what will make people stay on your forum (what can it offer that unique verses other forums or things for them to do online?).
If its not popular, how will you cope with that? (are you happy to maintain a very quiet forum for months-years?).
If it does get popular, how will you cope with that? (Do you like dealing with people? Have you moderated other communities before? Can you cope with disputes and issues? Can you admit mistakes when you make them?).
99% of the work with a forum is community building, its not technical. Its about being there to interact with people, making things nice for people, working to add features people want, and ensuring the space is one that they feel safe and comfortable to be in. The closest thing I can compare it to is running a hotel or a restaurant; the building, the kitchens and the tables are all important, but its the food and the service that really matters.