I don't have VIP and do everything mentioned by Peter and Stephen, although I miss many of the matches.
The main 'expense' is bidding during the transfer windows, so I'm careful not to waste my bid on players that I probably won't get and will often wait to see how many bids are on a player before deciding.
Having said that I can sometimes spend 50 credits in a transfer window but by being careful most of the time the general trend is upwards. On average I gain about 20-30 credits per season.