i've run campaign in TJ few days ago at first i spent $25 and i got 1 conversion so far
but when i add more budget with same banner i got loss
did you guys know what the ideal $$$ number of budget for 1 campaign? (day 1 i use $25/campaign and day 2 i use $50/campaign)
should i start with the lowest bid they advice or the highest bid? (i'm using highest bid in this case)
any advice would help me 
cheers
If those small budget increases damage campaign ROI you should figure out why.
I can think of two main reasons:
1. You are getting traffic from new placements that are performing less well
2. You are bidding CPM and your banner CTR is degrading
Since you are bidding high, I imagine it is 1. that is doing this.