I want to be able to hit +39 to UMD so that I can reliably (100% of the time) use heal scrolls by level 16. This is because after this point I can still use exceptional siberys shards to swap feats and I have three feats I want to swap out by this time (the mark of healing chain). My character is a halfling rogue with a base 8 Cha score and max ranks in UMD. Here is what I have so far:
19 ranks
8 base Cha: -1
+2 Cha tome: +1
+6 Cha item: +3
Golden Cartouche: +3
Greater Herosim (Planar Gird): +4
Total: +29
So I need to come up with another +10 somewhere before I'll be happy with swapping my feats. I need to do this without relying on other players to always be around since you never know when you might need to join a PUG. So what can I do that is reasonably achievable by level 16? I know I could spend some points on Rogue Skill Boost, and I'm considering doing that, but I'm strapped for APs and would like to see if I can hit it without doing that. Swapping a feat for Skill Focus: UMD is a possible consideration as well, but I'd rather spend my feats on combat.