If you want to boost your overall ini, then yep you need one for all. But probably best just to start with your Move 1 slot.

Is it worth it to put one on every nin, though?
Overall initiative is pretty important for barriers. . . but later on, manual barriers would be better than passive barriers. . especially with Roshi and stuff. . . .eh. . .

just go 3 or 4 ini chakras first before u go for any other chakra

All depends on your play style and team, if it's ini based then definitely. However with those rainbow magatamas coming, I believe they'll bump up your ini a fair amount also.