It depends on a whole lot of contributing factors as to what size rig is necessary to get the job done. Me, I like powerful amps not so much for the volume but for the headroom and tone/dynamics that should come with them.
I played a gig in a large auditorium last week with a single fifteen and a 350 watt transistor head. It was fine, but the audience was seated and we weren't playing loud. There is no way I would go out with my blues/rock band with just a fifteen. The difference is the rig that the guitarist uses and the power of the drummer, then of course is the PA providing bass DI and what type of venue is it?
I don't think there is a hard and fast rule, I think you find what suits you and then adapt to it. Many many years ago I toured the country with a 200 watt GK RB400 and a single fifteen and no PA reinforcement, the memory of that rig regularly farting out continues to haunt me. At the time I did not know any better, but a lesson learned the hard way is a lesson well learned. These days I wouldn't contemplate doing a pub gig without either a 215 or a 610 cabinet (and in my case coupled to a decent tube head). I might not need all that power but the headroom and tone is there and I use the volume control to turn down to the requisite level. IME it is far preferable to have too much power and turn down than have too little power and turn up to a level that is not optimum for the amp/speaker combination.
To get back to the OP's original question, and his financial limitations, I would be looking at a reasonable 8 ohm 410 or 212 (as he mentioned), then try to pick up a cheap second hand amp (older Peavey, Hartke, GK or suchlike) until such time as the budget allows an amp upgrade.