Joria, I think playing for tips without a lot of performances racked up would have been a waste of time, yeah, but since you couldn't have parties until you made Rock Star it was essential to max the career as fast as possible for the challenge.
I'm embarassed by how long it took me to realize the stadium concerts paid a lot more than theater concerts. A lot of time wasted there, and not enough time to really fix it. For what it's worth, I think the payouts are random - I had a theater concert pay 450 while I had moodlets totalling +200 and all my needs high, and one pay 800 while my moodlets were down to +25 and my needs were getting down towards the middle.
My biggest mistake? I ended up getting my performance totals up to just under 1500. The last Saturday, I went out to play for tips, and the first couple tips I got were on the order of 5500 simoleons. I panicked, and started performing songs again to get the total up higher (I thought there might be a breakpoint at 1500), figuring I'd look for an audience after Sunday's parties, and never found one. I think if I'd been patient and tried to get a bigger audience at the tip session I bailed out on, I'd've gotten a double tip eventually.
I'm also irked by my last party: one of the guests walked in the door, said "Fun party? Not. I'm leaving." - and then didn't leave. That was still enough to make the party count as a "modest success". On the bright side, I noticed that I could have my utility sim herd the party guests while my rock star played guitar upstairs the whole time and still have epic parties.