If you're comfortable with the six you have I'd stick with them and get to know them really well. Try all the different shots (FH, BH, overhead, rollers) with each disc and get to know their capabilities and limitations. Play with some better players so you can see which throws they use and possibly incorporate them into your game. Get a backup disc for whichever ones you find invaluable. Hopefully your si include drivers, some mids and a putter, if not fill those holes.
Once you know them front to back, determine what shots you'd like to add to your asenal, then use Joe's Flight Chart and advice from other players you trust about what discs to consider adding to reach your goals.
The first disc you might want to get multiples of would be your putter. Onc you've found one that feels right get 3 or 4 to practice with. Try to pause between each practice putt and set up just like you would for a putt to win a match.
Once you know them front to back, determine what shots you'd like to add to your asenal, then use Joe's Flight Chart and advice from other players you trust about what discs to consider adding to reach your goals.
The first disc you might want to get multiples of would be your putter. Onc you've found one that feels right get 3 or 4 to practice with. Try to pause between each practice putt and set up just like you would for a putt to win a match.