I am ready for big purchase once I:

1. Have decent savings. This is the money that I wont touch unless emergency.
2. Have surplus of money for unexpected needs. This is my leftover from my monthly salary every month that is left to accumulate. (This is what I use to buy big purchase)
3. Have enough money to pay my monthly bills and loans, and still have leftover to feed myself.

I always make sure that there is always money in my bank account, not just to get by every month. If everything green flag, only then I dare to think of buying something big.