OP I'd recommend a good multi-vitamin. B12 is a serious need and a deficiency can really fuck you up like PERMANENTLY. Even if you are eating healthy fast food a lot of the vitamins and minerals get processed out.
The guys over in Health and Fitness can recommend a good multi. You don't need to go crazy expensive like an Animal Pack unless you want the convenience.
www.drumlib.org is like pricewatch.com for supplement pricing once you find out what you want.
When I was a bachelor I cooked a lot of ground 97 and 99% lean turkey and ultra lean beef. I didn't like ground chicken too much. I'd get chicken breasts though pre-prepared so I could just grill or bake them ahead of time.
Canned tuna and a little miracle whip lite was good in whole grain pitas with veggies...I liked adding salsa to them.
I'd have a few steak day/nights too.
A lot of this stuff is easier if you prepare it all in one night like say when you are waiting for your clothes to wash anyway. Get a bunch of plastic containers then freeze lunch and dinners complete. Some veggies can just microwave with the main course, some your can grill ahead of time then reheat for some extra flavor.
A good salad with any of the above on it is also easy, healthy and has the benefit of taking a while to eat so if you are a foodie type it's satisfying. For me the quicker lunch or dinner is over the better.
One of the cool things of making good lunches and eating them where others are around is it attracts women that are foodies. Once they see no ring, they will usually say something like "oh your g/f must be an iron chef (or whatever), what a lucky guy...I wish I had someone making me that..."
"Actually, I live on my own [she's pretty much assumed car and job checkboxes are covered now to ]; I like to eat right and for it to still taste good. Surprisingly this took very little time, want to hang out one evening or afternoon and play in the kitchen?"
When I was single and ate in the company lunch room and the food court at times, it became pretty fun the attention my meals got. At the same time I was a hardcore gym rat so it added another level of "you can eat stuff like this and still look like that?"
Good food doesn't have to taste bad, be hard to make or very expensive. I will say good fruits and veggies and real meats are a bit more costly than the 10 for $10 stuff and even the 3 for $10 meals probably some of the time. Definitely cheaper than eating out at any fast food place though and more tasty.
oh, if you invite a chick over to have a kitchen date, make sure you have some condoms on hand...just sayin'