As a (currently 9th level) Infernal Binder I get an Imp as a familiar at 7th level. It has Charisma of 14. I want it to use wands I craft to cast spells that I would know. I assume it needs Use Magic Device to do so(?). If so, does it use my skill ranks? Does it get skill ranks of its own?
I don't plan to put any ranks in UMD for myself, but if I do is that an option?
Yes the familiar gets the same skill ranks as you, but uses its own (non-rank) skill bonuses.
Note also that the familiar has its own class skills - it doesn't use yours.
The "familiar uses your ranks" gimmick is a nice thing to exploit for some fun gaming. Not very powerful, just fun... and lets face it, fun is the goal of gaming.
For example, while you have your imp on your shoulder you effectively get 2 rolls for most skill checks that aren't physical (physical, like crafting or swimming). For example, you get 2 knowledge checks, 2 perception checks, 2 spellcraft checks to identify a spell, etc. Plus your Familiar makes some of the Self-Buff spells more useful, like the polymorph subschool (Dire Bat steed).
For each skill in which either the master or the familiar has ranks, use either the normal skill ranks for an animal of that type or the master's skill ranks, whichever is better.
Even if you weren't planning on it, I'd suggest putting a rank into Use Magic Device every level if this is your plan. With Int being a primary stat, that shouldn't be a problem.
Now, outsiders do not specifically get Use Magic Device as a class skill, but their list does include a bunch and at the end it says "plus 4 additional." Those four for the imp are Acrobatics, Fly, Knowledge (arcana), and Spellcraft. So the standard imp doesn't get UMD as a class skill. You could ask your GM to change out one of those four for UMD, but that would still mean a static score without using your ranks.
Eagle's splendor with the Extend Spell would help, as would getting a Cha-boosting item and having the imp wear it.
I usually just use Improved Familiars in a roleplaying sense of just being better at GTFO-ing. I've always assumed you could use Familiars with hands for wand use, but what is the build to do this feasibly? And what familiars make the cut? You need training in the skill, yes, and you would add its mod, but activating an item is still DC20. At 7th, no class bonus, the imp has +9 (you are trained, making it trained). It's less than 50%, so not reliable in combat, anyway.
The Evolved Familiar feat allows you to take the evolution that grants your familiar a +8 bonus to a skill of your choice. That's a good way to boost UMD.
