It really depends on what your current setup is...

When using fingers your arrow has mostly side to side movement.. and your arrow rest is normally designed to account for this movement. Normally this side to side movement allows the fletching to clear the arrow rest.

When using a release.. the arrow has mostly up and down movement.. and you need an arrow rest to account for this movement.. Also the arrow is normally being forced down into the rest.. and any fletching contact will result in very erratic arrow flight.

Depending on what kind of rest you are currently using.. would determine if you'd be better off sticking w/ fingers until you can afford a new rest also.