As many as you want to and are interested in leveling.
Personally, I plan to invest heavily in maybe one or two crafting trees then make sure I have points distributed where I want them in various class, weapon, armor, guild, racial trees, etc. then use the leftover points to dump into random crafting stuff here and there. I think I read that the total number of skill points you can get by leveling, getting all the shards and from quests is something in the area of 200+, maybe upwards of 300. I could be wrong though.
Either way, you generally have a lot of points to play with, plus you could always respec if you find that you spent points on something you don't want anymore.
Thanks for the info. I'm prob going to do something very similar now I just have to decide which 2 I want to go with. I guess I'll try to keep all the mats I can find just in case I want to switch down the line.