I would say keep doing what you're doing...Your legs are getting stronger and you are able to push higher gears at a very nice cadence pace...When you go through all the cogs and can do 80-90RPM in all of them then I would say try the same process all over again but try to do your base at 90-95 and your spin at 110-115...

I would say get also get a computer with cadence. Getting one has helped me stay in the cadence zone and not slack (before I had a Vetta computer with no cadence).
I got a Cateye Astrale 8 for $34 and it is really worth the money.