Cheap runs to collect?

Hi everyone! I'm relatively new to collecting comics and mostly read collected editions, but I've been attending conventions that sell a lot of single issues and I think it'd be fun to complete and search for a run. This is A LOT more expensive than collecting trades (at least in Australia), but I'm definitely interested in expanding upon my pitiful collection of singles.

What relatively inexpensive series would you recommend I collect? I see a lot of 90s stuff for pretty cheap so I imagine those are a good place to start, but I'm looking for series from any era that are high quality but also really common. I'm interested mainly in marvel, DC, and Image. Thanks very much!