I'm not sure if this is the kind of info you seek, but I started out many, many years ago (1972) in a similar situation. I owned a Mitchel 300 spinning reel and a six-foot UglyStik spinning rod and very little cash. My bassin' mentor took me fishing in his jon boat, supplied me with some what I considered ridiculously large (4/0) hooks, a handful of Creme rubber worms, and coached me on how and where to use them. The result was my first four-pound bass and a love of bass fishing that sticks with me to this day. Up until then I just fished ... no rhyme or reason.
Sorry to be long-winded, but I was trying to make a point. I love bait-casting ... and spinning gear. And with a tight budget, you appear to have a tough choice. First, I personally believe there are some quite decent bait-casting combo packages available for under $100.00 at Walmart, Dick's, and numerous on-line retailers. Or you can search E-Bay, Craig's List, and flea markets for good deals. But, in all these cases you will be faced with a depleted budget and no tackle.
The other option is to really examine the gear you have; maybe have an experienced friend you know take look at it. If you provide as much info (usually found on the rods) and brand/model in this forum, you may also get some really helpful advice. You may find your rods, reels, or both are adequate and you can focus on getting some new tackle. Even if you need a new rod or reel you still have bucks left over for some terminal tackle, a few packs of soft plastics, a couple of spinner baits, and a couple of lures.
The worst case is that your gear may be unsuitable and you are faced with option one.
i suggest you don't be in a hurry to blow your budget on a bait-casting outfit right away; there is a lot to enjoy about bass fishing using either style and personally I can live with either - as long as I'm fishing. Then while you enjoy fishing with the gear you have, you can start saving (and researching) the bait-casting rig you will purchase in the future. To me, the most important thing is to get out there and enjoy fishing!! A lot of us can't afford all the fancy gear but I'm willing to bet I have just as much fun as anyone here using the stuff I have. It ain't about the toys - it's about learning to outsmart a bass!
Good luck.