Having a slight conflict with DH at the mo. He thinks we should be saving buying toys for birthdays and Christmas or other special occasions so as not to spoil DD. I think this will be important when she's older, but at this age (21mo) I think carefully selected toys are more about helping dd's development - and there's some self- preservation in there too, ie toys that will amuse her for anything longer than 5 mins without needing our input are A Good Thing.
In general we try to mostly only buy toys at Christmas/Birthday. However DS's birthday is end of January and that is relatively very close to Christmas - so he gets a few things in the Summer too. In the early years, they are passing developmental milestones very quickly - so you want some toys that keep up with that (especially as they get to about 2.5 years old, I think - they are suddenly not babies or even really toddlers any more...).
It is very personal, though. One of my friends seems to have purchased the entire contents of Toys R Us for her little girl.... I wouldn't say the child is "spoilt" in personality (can they be at 3?), but she certainly doesn't seem to "want" for any toys...
Ways round needing to buy too many toys too often: - join a playgroup (lots of toys there). - take turns hosting friends with similar age children (we do this amongst my NCT group): they love playing with each other's toys and in each other's gardens. - put some toys away and then swap over (bring them back out and put others away) every couple of weeks: like having new toys again. - go out lots and do activities (spending money that our would otherwise spend on toys): swimming, toddler sense, sing and sign, music classes, tumble tots, soft play etc.... We go to the park and play there a lot. - buy arts and crafts things instead of toys and use household objects to make new "toys".
We're starting to slow down a little with DD now, coming up to 26 months, as the toys are starting to get more expensive and she is starting to expect them at times.
Up until now the toys have been second hand or else little bits and pieces from the supermarket. DD loves books so I often get her one for a couple of quid if I feel the need the 'spoil' her a little as I see books as educational (yes I am pretty good at finding loop holes to justify myself at times )