There will always be more buyers/users then there will be makers, so I wouldn't worry too much about how flooded the industry is. A large number of knives I make are sold to people I know, and/or repeat customers.
Just do a good job, put your own spin on it, and price it reasonably, and you should be able to sell what you make after you get the hang of it.
As for tools to start out with, every maker should have a way to make holes and cut steel. A decent drill press, IMO is a must, and arguably one of the more versatile, most used tools in a shop. Also, I personally I prefer a bandsaw over a cut off wheel on an angle grinder. Less messy and more precise, and probably a bit cheaper in the long run. Get a used portaband and mount it vertically to your bench. Speaking of which, you also need a good work bench. I've got some videos on my channel on how to make one out of common framing lumber for about $100 or less if you wanna go that route.
Now, a filing jig will get you started fast and cheap, but I'd also start thinking about a 2x72 grinder. There are lots of options these days that can run anywhere from $500 to around $5000. Personally, I scraped and saved for parts to build a NWGS with plans from Tracy Mickley at USAKnifemaker.com. Bough a little scrap steel here, a used motor there, a few nuts and bolts after a couple trips to the hardware, one or two parts from ebay... etc....
And then I took my time and built a little of it at a time until I finally had the frame done and was ready for wheels. Now days you have a lot more options for decent quality wheels that won't cost as much as mine did.
If you can find a good price on a used motor and some scrap tube, you could probably build a flat platen NWGS for $500 or less and have a grinder that's expandable/upgradeable.