Well an OD pedal is not really an "effect". An overdrive pedal just jacks up the guitar level hitting the amp harder. They're not really "distortion pedals" because they're not like an amp in a box. They're signal boosters. This also tightens up the sound some making things, well, tighter, more articulate, as well as pumping up the gain because it's driving the preamp section harder. They go really well with lower gain amps. Some OD pedals like the classic Tube Screamers and Boss Super OD have some dirt you can add as well. But to me they sound best as simple clean boosts. Keep the "drive" low but max the pedal volume and hold on tight. You're gonna be jamming those preamp tubes with hot signal. All those gay ass 70s/80s metal maniacs like Randy Rhoads and Glen Tipton and CC Deville and so on.....low gain amps slammed with overdrive pedals.
You can get used Boss Super Overdrives and used Tube Screamer TS-9s for next to nothing. Maxxon OD is good too. Try one out.