save your skill points until your skills cost at least 20 platinum to raise
I have mixed feelings on that. I followed that advice, and I'm now level 19 with 80 skill points sitting in reserve. My highest skill is evasion at 27, and most of my other skills that I use are in the 15-20 range, and it costs anywhere from 4-7 or so platinum to raise a skill potential.
The problem is that by saving skillpoints like that I've had to do literally
hundreds of quests to get enough platinum to keep my skill potentials up at a reasonable level. (50-70% mostly) I'm sure I'll benefit later on, like the advice goes, once it costs 20+ platinum to raise a potential...but I kind of had to suffer a lot along the way.
If you're willing to do hundreds of quests, yes, saving your skillpoints for later on will ultimately give you a more powerful character. But if you're not, it's not like the game is so difficult that it's absolutely neccessary to go to the trouble. So I'm not saying don't do it...but don't feel like you have to.
I think it will also make a big difference what sort of charcter you want to play. Personally, I chose a warmage, so I'm investing in both melee and magic skills, plus I use a lot of ranged combat, and I've also taken up gardening, pickpocketing and performing. So altogether I have about 20 skills that I'm using. 6 skillpoints per level might not have been enough for me. But if you're playing a straight mage or only a sgunslinger or whatever, 6 skillpoints per level might be enough that you wouldn't really ever need to do quests for platinum even if you started spending skillpoints right away at level 2. But on the other hand...with 20 some skills, even havign used a couple wishes, I'm now at 36 platinum to buy a new skill, so that's 15+18+21+24+27+30+33+36=204 platinum just on buying new skills. If you want that many skills and you're planning on hoarding skillpoints too...that's hundreds of hundreds of platinum you're going to need. If you were to only use platinum to buy new skills and spend skillpoints to keep their potentials up, even then that's still a couple hundred quests. Hoarding skillspoints, maybe four or five hundred. Some players might be unwilling to do that.
So overall yes...hoarding skillpoints may give you a more powerful character come end-game, but it may come with some costs too.