I'd recommend reading the Clan pages and descriptions and PMing the leaders of the clans that appeal most to you.
Each clan is a different "flavor" of the metagame- different paths you can take to pursue different parts of Warlight. For example, The Lost Wolves and The Royal Falcons seem to enjoy the social aspect of Warlight, focusing on diplomacies and internal clan politics and talking. Then there's the Poon Squad, who like being a little bit... unorthodox but also similarly enjoy hanging out together and playing team games, often on interesting settings (they don't like games with long boot times). Illuminati seems to be a gathering of players who constantly strive to get better at the game, especially at 1v1s, while apex and [Lynx] are more "elite" clans than the rest and seem to be more competitive about things.
But as a member/leader of CORP, I feel most qualified to speak about my own clan:
Our clan's view is that we exist solely for our members. It's a bit stripped down, perhaps too meta, but we believe that our clan should be a platform through which members can pursue their own interests and develop as players. So we're both a roleplay clan and a strategy clan- to us, the goals themselves don't matter as much as how hard we work to achieve them. We focus on having regular interclan and intraclan games to better connect as a clan and to collectively pursue our goals. Specifically, we run a ladder/league system (that's been on hiatus this week as I renovate/automate it), have regular team-games against other clans, have regular tournaments, regular diplomacies, and just a whole lot of games that sometimes backfire and overwhelm people (>_<). We've also got a sub-clan organization system that's based around people getting together around specific goals (like getting better across the board on strategy or playing more historical/fictional scenarios in diplomacies) and working to pursue them.
In simple terms: CORP, if anything, tries as hard as it can to be a clan worth joining.
If, after reading that, you think that CORP would be a good fit for you, you can apply through me. Diplo players just have to shoot me a PM with a link to a diplo game they're particularly proud of (not one they necessarily "won"). Strategy players just have to set up a 1v1 against me on a template they consider "strategic" (can be as mundane as Strategic ME 1v1 or as exotic as a limited full distribution template with Bomb Card and No-Split Mode on a map no one's even heard of... just as long as you personally can say confidently, "Yep, this template is strategic."). If you do that and I find you to be a good fit for the clan, expect an invite and a welcome message. :)