Just for perspective @Vattic, I get about 20ish join requests a day from newer players for my guild, the Raiders of Ravenloft. So don’t feel discouraged if the first couple of guilds don’t accept you. And you’re right, it’s hard to tell whether someone will be active. I’m not super strict on the 2k trophies, but in the absence of other information it’s a rough indication of interest and activity from a player. Given the guild composition and members’ desire to be strong, I’m sort of forced to restrict membership to higher level players.
I’d suggest finding a guild with some activity, but a number of open slots and grow your heros first. If the leader has an active gift count or shows up on the overall leaderboard, then you at least know he or she is still playing and so will respond to join requests. As leader, you sort of have to respond, otherwise your guild page is completely taken up by join requests and you can’t see anything else in chat:)
If you like your initial guild, great. If not, once you’ve grown you can move to a different guild. It honestly doesn’t take all that long to hit 2,000 trophies if you like the game and play a lot. If you’re more casual, than it’s a longer road to grow your heros.
Hope that helps and that you find a guild to your liking.