Now that I've finished doing RTK I have a (mostly) set plan for whats going to happen on my future studies.

For now, I'm going to:
- Keep up with reviews.
- Try to finish Core 2000 and bits of other interesting Japanese related studies on Smart.fm
- Finish Tae Kim's grammar.

After doing this I would like to move into:
- Still doing RTK reviews.
- Finish Core 6000. Other side Japanese study applications included.
- Start mining for sentences.

So basically what I'm going to do is put off any major sentence studying until I've finished the first step.

Basically, would this step be a good idea or should I start sentences first and move on from there?

You could do sentences while you're doing the others, maybe just start small (like 10 sentences every day or two, from Smart.fm/Tae Kim) and get a feel for it.

When I started with sentences, it took me a while to get a style I liked for my cards. So maybe starting slowly you can work out what works best for you, so by the time you want to start focusing a bit more on it, you'll have found a style that works for you.