+15 skill items are relatively easy to find...you can pick them up in vale slayers, or even in orchard slayers with a loot gem. They are also fairly common on the AH.
By the time you get to lvl 10-12 would be a great time to farm orchard slayers to pick up a set of tapestries for a minos helmet. Along the way, you will no doubtedly be able to loot a +6 Con, GFL, +6 int item, as well as 13-15 skill items. You can also get sup pot 6 and a magi item if you didnt loot one already. In ADDITION, you should accumulate a nice little pile of plat as you do all of this.
This build will have no issues doing orchard slayers as soon as you can step into the orchard. Level 13 will be when it becomes easier, as you will have access to disintigrate, which can make a couple of the bossfights alot easier. The blackbones can easily be taken down with melee or skipped before then.