First of all you should get to know every single skill perk in the game, with this picture:

You can get this perks not only on weapons but on armor as well (despite what is said on many databases).

First of all keep in mind that these bonuses SUPPOSED to work like this:

• One perk per item
• The same perks from different items doesn’t stack up

Second important tidbit is that before you go ahead setting up your build with specific skill perks, watch this two videos:

As you see, due to many bugs and bad design some perks doesn’t work at all (like Fireball one), or are broken like “Empowering Shooter’s Stance” and give too much (for how long though?..), or maybe work as intended like Insatiable Gravity Well.

Thus you have to find out if perks you want work at all or right, before you set out to make your build.