Gaussian's are good but the CL-5 excavation pulse or whatever the forget it's called is better I think.
But miner IIs are the best, until you get a barge with strips.
I too do some mining here and there. Your best bet it to start training for a retriever. Takes about a week or two, and it's well worth it. It has around a 3256m3 cargo hold and you can make something like 60-200k isk per 3 minutes mining, then you have to haul it back which adds a few more minutes on (half hour or so if you add it up).
All in all mining and industry are the real money makers in eve, once you really get some high quality gear. With mission running coming in second and everything else after that. If you can get into industry (it takes a long time to actually become effective at it) you can really start bring in the isk.