Should I start playing or wait?

Trying for a few days to get onto a realm where my friends are playing (Tonberry).
Been trying hours on end to do so. Should I just wait until the game dies down a bit and the server unlocks or should I play another server? What are the cross-realm features like?

Tonberry's been listed as a Congested server, meaning there are currently restrictions on new characters and player transfers. If you're not already in, you're not likely to be getting into the server any time soon.

Cross-world features include dungeons/trials/etc, most instanced content; you're free to form a party across worlds and run any of the duties together. Through the Party Finder feature, you're able to form parties outside of these instances, the benefit in this case mostly just being that you can still chat with friends in open world content.
Some of the limitations will be not being able to participate in any open world content with a cross-world party (you can chat, but they're still on another server, so you can't get together except for those dungeons and such). Won't be able to trade items or anything. May run into some troubles if you're required to run something solo for a story quest (may force you to drop the party for the duration of the solo instance). May also be limited by parties being a max of 8 players; you or your friends may have difficulties staying in touch with everyone.

So mostly kinda depends on what you want to do when playing with friends.