thanks a lot deep dai. what about compressor? I hear that's quite important too.
I have boss cs3 compressor. I don't normally use it. it comes in handy occasionally. Its not a must. I use two amps :- My marshall jcm2000 half stack and my friends Fender tween reverb. I use my marshall for high gain music and when there is hi gain i dont require a compressor sustain pedal because the hi gain overdrive of the amp is already sustained enough. however if i'm playing the tween reverb for a less hi gain sound i use an overdrive pedal for overdrive(because the fender tween reverb doesn't have onboard overdrive) and then I'll add the Boss cs-3 to it for solo tones only to add more sustain and up the volume level a bit (for solos). David gilmour is a fan the boss cs-3. it's good especially if you want a long sustaining tone without heavy distortion/overdrive just like david gilmour's sound.
I say invest in a good tube amp and a decent guitar and thats all you need. pedals come after that. It really depends what style you're playing.
If your trying to virtuoso your sound (satch, vai, eric johnson, petrucci) they use a lot of color as in add chorus/flanger, reverb/delay, compressor sustainer and usually they have a rack unit for most of those which runs through the loop of an amp head. they control the rack unit which usually backstage with an on stage footswitch control board(a big board with a bunch of footswitches). but pedals do the trick as well for less budget.