Hi Aiden,
I have found that the cheapest that i can make a full working saber from scratch is around 75 bucks, which includes seoul LED and sound card. Best way to go about it is start at custom saber shop forums and read like crazy. Tim is the owner and is extremely helpful and they have every write up in the book on what you would need. I would suggest starting off with a sink tube saber because those are the most cost affective. You can make one for around 30 bucks for the hilt and after that, you would just need the starter led kit, heat sink blade holder and a sound card. I personally enjoy making the hilts from sink tubes rather than buying them because im one of those jerks that likes saying i made the whole thing myself (that and im poor and do not have 100 extra bucks to be spending all willy nilly),
I also like the look and they can turn out really nice and only really need one or two tools to make them. (See below for examples i have done on the cheap)
View attachment 324924View attachment 324925
For the sound card the best bet is to get it from an old hasbro toy that you can find on ebay for 10 bucks or so and just wire it up. Im no electronic guru but it is only a few wires and step by step directions can be found for each sound card on the TCSS website. I dont want to fill up your post with useless info or direct links to parts you would need but feel free to PM if this is something you might be intrested in and id be more than happy to help!
good luck and happy saber smithing!