One I'm glad I caught early on when I started back in December; focus on a character's Character Ability section of their skill tree first. You don't have to immediately max it out, but at least unlock the first node or two with the handful of skill points you're given from the start. Worry about the Energy Cooldown tree last. Also, save your Canopy Coins and Skill Points for a bit once you have a character decently levelled and their skill tree decently filled. No need to splurge all that gold all at once. I like saving up a lot and unlocking a handful of nodes at a time. Just be wary you're not eating through too much of your money, though. Also,
don't use Theonite to unlock nodes. It's just not worth it. Use those shiny blue rocks to summon clones of people from alternate dimensions instead!
Bit more maybe-possibly-probably-not controversial tip; always begin a match by blocking. SGM has far less opportunities to evade attacks by, say, jumping than the PC/Console games do, so blocking is your best bet to avoid getting comboed from the start of a round. By all means, mix it up a bit and start with a grab or a dashback or even a ground combo on occasion, but your mileage may vary there in terms of success.