I’ve been building a small studio. I recently purchased a Line 6 Studio Pod UX1. I’ve plugged in a mic and my acoustic guitar with a Fishman pickup, but not happy with the sound from my pickup. When I perform the sound doesn’t bother me and people don’t even notice, but for recording I want a natural sound. I’ve tried using the mic for the guitar on one track and the vocals on another track, but I have to do them separately. I would like to do them both at the same time. The Studio Pod has a plug for the mic and one for the guitar. I’m wondering, can I use a mic in the guitar plug and what’s a good mic for the guitar without breaking the bank?
You could use a mic in the guitar input only if you also bought a female XLR to male 1/4 adapter AND your mic did not require phantom power. Still, this is less than ideal because there is no mic preamp.

As for a good, affordable mic for recording guitar, you have to get the Sure SM57. It is the most popular mic for recording guitars in both home and pro studios. It is about $100. There are cheaper mics out there, but honestly, this is the best bang for your buck mic. Built like a tank and awesome on guitar amps (I remember reading somewhere that 95% of electric guitar tracks were recorded with SM57s). My drummer dropped one of mine from 15 feet onto a solid concrete floor and still works just like it came out of the box (I have three of these mics and can't even tell which was the one that was dropped).
Just realized you were appear to be doing acoustic recordings with vocals. In that case, ignore my previous post. What you need are some solid condenser mics. They are fantastic on acoustic instruments and vocals. Unfortunatly, they also require phantom power, which makes your interface pretty much useless as I don't believe it has a phantom power option (even if it does, it would only have phantom power for one mic).