Modifying pedals is the first step in becoming part of the pedal building community. Here is a great place to get you started!
MXR Phase 90
The Script mod is an easy mod for any beginner. This improvement lets you switch between the original circuit, and a more vintage and dark sounding phaser.
MXR Blue Box
The C11 mod is an easy mod for any beginner. This improvement lets you switch between the original circuit, and a more opened and wild version of the fuzz.
ProCo Rat
This mod will give your distortion some thick low mids. All it requires is 3 Red LEDs, a DPDT toggle switch, and standard soldering tools and equipment. A great first mod for a beginner.