It's pretty easy. You get a lot of respec points from the quests themselves, 18 by the time you finish Merciless. Then you'll probably have at least 5-10 regret orbs you found by yourself. Two Scouring Orbs can be turned into a Regret, and lesser currency can be turned into Scourings (see
here). Then 1 Chaos Orb = 1 Regret, and you can easily trade these in chat or trade items for Regrets.
I've probably used like 40-60 Regrets at this point. It's not a big deal.
You shouldn't worry too much about the tree. The only advice I'll give is to get life nodes and evasion or armor, depending on which way you're going. If you ignore these you'll screw yourself over since you'll then have a hard time just farming for currency (if you're too high over the area monster level, less currency drops). Whatever path you take, just get all the life that's on the way, or go out of your way a node or two to get there.