Hi, I'm a high schooler with no budget, but i'm trying to get better audio in the short movies that I make. I'm getting the $150 rode videomic with the rode boom pole, to substitute for the in-camera microphone of my $200 miniDV cam i use right now. However, my miniDV cam doesnt have a mic input and I'm planning on buying a new miniDV cam that does have a mic input ($270). Will the audio from the boom pole thats going into the camera be substantially better than the one from the in-camera mic of the one i'm using right now?

If you can get the microphone on the boom closer to the sound source/subject than your camera can go, yes, it will be much better audio. Even if the camera is very close, you run a high risk of the cam picking up sound from zooms, switches, and operator. Moreover, the Rode will have a much tighter pickup pattern. You'll want to practice with the Rode and boom before using in an actual production.
Welcome to the forum, BTW!

Will the audio from the boom pole thats going into the camera be substantially better than the one from the in-camera mic of the one i'm using right now?To echo DSE, answer to this is ... for SURE !! much better. Both quality of mic, and better positioning. Audio should be a real quantum leap up with the Videomic on a boom pole.