DFA and familiars

[Efrate]

I know a DFA can select a familiar, but can one just take improved familiar or must they take obtain familiar first?

Assuming the latter, or maybe even the former, what are some decent choices?

I'm a LE DFA in Faerun FWIW. Imp is the go to from what I've seen, but I know Faerun has some setting specific ones. My roles are BFC and face more than anything, so anything that can cover in other areas or help me excel in my chosen roles would be great. Dragon Familiar seems underwhelming since it can never advance or do much of anything. A winter wolf seems interesting as well, not sure how I can have them hold a wand but I am sure I can figure out something, but the BaB req is a pain.

Is it worth the one or two feats?

[Zaq]

Improved Familiar requires that you have the ability to acquire a new familiar, so unless there's some super-obscure ACF I don't know about that gives a DFA a familiar, you have to take Obtain Familiar before you can take Improved Familiar.

Also, most versions of Improved Familiar refer to "spellcaster level" rather than "caster level," which might get dicey when you're looking at a DFA (as I recall, they count as having an arcane caster level, but they don't necessarily count as arcane spellcasters).