In most game systems (at least of those I’ve seen) and particular d20 systems, a player gets a number of points each level to spend on skills, often with 1 point for 1 rank of skill, or perhaps different skills cost different point. Other systems might have an increasing cost per rank. Skills are also often attached to classes, and you can only buy ranks in your class’ skills, or perhaps pay extra for other skills.
Dual20 does not do that.
Instead, what you buy at character creation is how the skill advances over the levels you get (specifically the level track that advances Stats, Feats, and Game Breakers), and you buy grades of the skill, from 1 to 3, though it can get as high as 4 if you pick the right Foundation, as mentioned in a prior post. Since you are buying grades of advancement quality and not actual ranks or bonuses, skills (and stats) can advance at different rates from each other, and need not be linear.
So each grade of a skill should be of comparable worth to that of another, but he actual numbers you need for dice rolling or other procedures can differ greatly, as needed for that particular grade of that particular skill.
You can also buy grades in a skill group, which grants you points to buy subskills, that are generally more specific or limited scope and applicability, in a similar manner as other skills. In act, all skills work this way, as they can be considered as a subskill of the Skill stat that every character has. Game groups can even divide up other skills to more specific components, or combine subskills if they just want to deal with one big general skill.
So an example of a skill group would be Crafting, which can have the various crafting disciplines within it, such as weapons, which could be further divided into various types of weapons or not, as the group desires. You can even have a group for Flavor skills, that don’t have much bearing on the main part of the game, but can be useful at very specific times, and gives plenty of flavor to the character as implied by the name.
One more thing, Grade 4 skills may have a better bonus than Grade 3, but that’s not their big differentiator, if you get Grade 4 that opens up new uses of the skill that usually have a magical or mythical nature. You may still have to wait till higher levels to use it reliably, and they will generally not be as flashy as a mage’s spells, but they are just a bit beyond what a typical mortal can do. With Grade 4 Weapon crafting you’ll be a legendary swordsmith perhaps, creating blades of unequal quality (perhaps used by kings or six fingered men) or even get a little bit of overt magic in them if you get skilled enough, with Grade 4 acrobatics you’ll seemingly be climbing on vertical walls with the greatest of ease. Etc. etc.
There are a lot of benefits to using the system like this, but there is one thing I’m not too happy with and that’s the inability to go in a different with the character’s skills without using character rebuilding rules. But perhaps a solution will come up, and even if it doesn’t I think the pros outweigh the cons for my goals with this system.
The Dragon's Basking Spot 
The D20 system and whatever the previous editions of D&D were are pretty much the only tabletop RPGs I’ve seen that have character levels.
Most games are point-build. You just trade in so much XP for a skill point, or whatever the system’s “feat” equivalent is. Though some have some sort of in-character requirement for training or something to improve skills.
True, though even in the point buy ones, you tend to spend X points per 1 point/rank/bonus of the skill, which is more what I was going for. Game designers would need to design all the skills and system math such that a +X bonus to one skill has the same power as a +X bonus to another skill. That’s what I’m avoiding here.