I’m not sure from where you got that figure of "1st 5 transactions." It’s actually 3 transactions for the activation bonus.
Do like this:
First 3800 is for a bachat campaign only. Just pay 3800 using setu on any of your credit cards, and that will count as 1 transaction.
For rest transaction, portals don’t matter. You can continue using setu or unipay, whichever makes you happy. The amount can be anything, but try to go for amounts above 2000 for the other 2 transactions.
It will look like this: 3800 + 2000 + 2000.
This will complete your campaign as well as fulfill your eligibility for the activation bonus.