So much hearsay and conjecture. IMO don't upgrade until you max it out.
For instance, my RB30 instantly maxxed out the RB20 afm and constantly ran in R&R as soon as it saw any boost with more than 10% throttle or over 3000rpm. Maxxed out at 183rwkw.. also, the exhaust side of the 25 turbo maxxed out (can't physically flow the exhaust gasses coming out of the 30). Have since had the stock ecu remapped along with 550cc injectors and a z32 afm installed.. still have to live with the turbo falling over about 5800rpm till after xmas
Do the upgrades slowly, as and when you need them - this will also help if you come across any issues (too many changes at once makes it harder to diagnose problems).
The only thing I suggest going full hog on straight away is, if you know you're going to end up with a bigass turbo, bigger injectors, afm etc down the track, then don't waste money on a simple piggy back to start with. Just get a full ecu and go from there.