If they have everything in the Dojo you should be good to go on the clan front, unless you want to get super serious endgame stuff. Otherwise the matchmaking works just fine for completing alerts, dailies, whatever else you may want to do.
Enjoy the ride. :) It’s one of my all-time most played games, although I tend to go in long hibernation cycles followed by binging hard to get up to speed on all the content they’ve added since I was last playing.
One nice thing is it’s not predatory F2P as spending money is mostly just for shortcuts, content isn’t going to be inaccessible to you on any of the starter frames. And farming for new warframes, weapons, etc. is most of the fun for me, so paying for it kind of shortcircuits that aspect of the gameplay. If you do get into the game and start playing consistently, the “must have” for platinum purchases would likely be for additional Warframe and Weapon slots to add to your arsenal. Those are cheap, though, and as @NI1 said you can make platinum by farming Prime parts and selling them to others if you’re adverse to spending any money. Myself, I tend to just drop $20 periodically whenever they release new content I’m interested in which feels the same as buying expansions/DLC or whatever. That’s been plenty of platinum for my needs!