You can get maxell XL-II type II high-bias tapes at walgreens still, I'm pretty sure. If not they're available online as well. In terms of microphones you should definitely get yourself a shure SM-57- you will be able to use it on everything and you will always have a use for it, no matter how much great equipment you may end up getting. It's a dynamic mic and doesn't require phantom power, so that will be another plus if you're planning to run it directly into the 688.
I'm not sure what your budget is, but if you can afford it you might want to get a decent mic preamp. The amps in the 688 are not bad, but they are a little on the noisy side, which will make it hard to record quieter sources with a lower output mic. An external preamp would enable you to put a lot more gain on the mic without pulling up your noise floor, and you'd have the added benefit of being able to use condenser microphones that require phantom power. This is all you really need if you are recording yourself one track at a time- if you are recording multiple instruments at once you will obviously need more mics.
In terms of cheaper equipment that you might find useful- Studio Projects' VTB-1 mic/line preamp sounds remarkably good for how cheap it is- about $100, cheaper used. This was all I had for about a year, and although it's nothing special it certainly won't stop you from making a good recording.
You can find a decent budget condenser microphone for around 100 dollars, but I'd recommend waiting to buy a slightly better one- a marginal condenser is something you will end up replacing if you keep doing this. Having said that, if you find that one is really necessary, M-Audio's nova is more than usable, and can be picked up used on eBay for about 50 dollars. Jon O'Neil's Naiant studio store (
http://naiant.com/studiostore.html) also offers some excellent self-powered small-diaphragm condensors for 30 to 60 dollars- you won't be able to use them for everything, but they make great room mics or stereo overheads, and you'll be able to find a use for them for a long time to come.
Best of luck with everything- I think you'll find that as long as you take care to understand why you're doing everything your doing and read your manuals it's not nearly as complex as you might think. It's possible to get great sound with marginal equipment.
Theo