I'm sure this gets easier when I can get later to where they can all be respecced? Have a hard time seeing getting all the various combo's yall speak of. (Vamp+retribution+earthern shield thing that got nerfed, but aero for teleport and poly for fly, and ........... list goes on)
Early on you should probably spread your points and get some utility on everyone. Doesn't have to be ALL the utility, but some of it, having wings on chars that need to move, various buffs and armor regen spells on casters, this kind of stuff. To make a not shitty build, all you really need is to max one skill for damage purposes that fits your char(so warfare on anyone phys for example, or scoundrel if you're backstabbing, or huntsman if you're an archer, the obvious ones).
Past that, you can put everything else in random stuff and the char will still be good. If you want to min max damage, you'd want to max another specific tree and only take the bare minimum in other stuff relying on items giving +skills to get your stuff, but honestly that seems super not worth it the way damage seems to scale anyway. The thing to remember is for the most part, you only need 1 or 2 in a school to learn all relevant spells. 3 gets you some of the more advanced spells but unless you specialize in it, you'll rarely need that and they only unlock in act2, and 5 gets you the ultimate source skill in that school but realistically you only need one of these since source is limited and they cost 3memory slots.
But yeah early game don't spend all your point in your main tree necessarily, you'll have good damage scaling from gear+main stat from attributes anyway, so just grab all the various schools you want, and once you have all your basics, that's when you start dumping into a skill for the passive damage specifically. I'd also recommend getting some memory points early on to fit all these skills, you can respec out of them later once you get enough memory slots from normal levels.