It won't help using a better mike really, Laptops and cell phone cannot really produce good audio using the little jacks,, One thing is it's real hard to logically set proper levels with the interface they use. Then they normally compress and "auto level" the track.
I have been experimenting with recording myself and the best solution is to either record to a laptop with a proper audio interface or use a hand held recorder like my Tascam DR 40. Then simply sync up the audio in Vegas later.
It's been easy to do as I always have a count in that records to the on board or camers's audio as well as the Tascam.
I just did a shoot with 4 cameras. They all have audio tracks that I can use to sync the videos. I don't worry about the quality as long as they capture that count in clearly and at a decent level.
Then I captured my Voice and my guitar live to the Tascam. I dropped that back in to Cakewalk and exported a high quality audio track. Now I drop that into Vegas and once synced up I can delete the other low quality tracks.
Next I'm going to try recording directly into Cakewalk with my audio interface.