Like other have suggested, read How to Brew before you start buying equipment. The fact that you haven't bought a starter kit and are asking questions first is a good sign.
You've got a good start already having a kegerator. It won't take much to adapt ball lock kegging equipment to your sankey equipment. Don't bother with kegging in sankeys. The hassle to disassemble and clean/sanitize them is enough to push you away from the hobby at this point. Look for some Cornelius (style) ball lock (more common than pin lock) kegs and replace all the gaskets if you buy used ones. Assume these will be around $50 each used.
Do you have a turkey fryer? I used a cheap turkey fryer burner for my first 10 batches and it was good enough to boil 10 gallon batches with simple propane 20lb tanks that you might already have. Check craigslist, etc.. I've since stepped up to a Blichmann hell fire burner. This will work on propane and natural gas. I don't plan on ever needing to replace this. Fuel type (flame or electricity) will vary. Think about what you have available to you.
A 15.5 gallon keg with top cut out makes a great vessel to boil in. Add a $15 drill bit and a $40 ball valve/fitting and you now have a boil kettle. Add a $20 bag and you now have a simple BIAB set up. Don't burn your bag (only heat before you put the bag in and after you pull it out) When you do pull it out, consider a pulley/hoist. This setup will allow you to make 5 gallon biab batches now no problem, and allow you to step up to 10 gallon batches (boil kettle volume) in the future if you want to buy a mash tun to hold more grain (100 qt coolers are cheap). I jumped to all grain, but you can easily do 10 gallon full volume extract right now too. Do you have an old sleeping bag? wrap it around the keg during mashing (if doing all grain) and you'll be good.
Do you have a good handheld thermometer? A good digital pen type thermometer is another multi use tool that isn't going to grab and rip your bag when you pull it out of your kettle (hint...) A big ass spoon is great to have too (long term multi use)
Hop socks in the boil kettle work and are cheap. Pumps are nice to move wort around for features like a counterflow heat exchanger, but you don't need one to start. A 25' copper immersion chiller will be fine to cool 5 gallon batches down to pitching temps (make sure it reaches down into your kettle, 25' ones typically don't fit down into keggles) . I use my original one in series with the counterflow chiller now to quickly cool 10 gallon batches from boil to 50F.
A brand new food grade plastic bucket works fine for a fermenter to start out with. They're cheap, easy to clean, and can be repurposed after they've retired (grain storage, wash bucket, etc..) Get used to taking gravity samples during fermentation. I do this easily now with a welded in bung in my stainless fermenter with a ball valve, but looking back on plastic bucket days, I'd suggest a simple wine thief where your thumb holds a vacuum (easy to sanitize) This is just me, but I don't recommend commercial plastic fermenters. If you're gonna spend money on a fermenter, go stainless. You don't need to right now, but when you do, consider going with a commercial sankey keg. 7.5 gallon for 5 gallon batches (if you happen to stumble upon one), and 15.5 for 10 gallon batches. Cheap, rock solid, and will last forever. Simple way is to use a carboy cap with airlock and dip tube. Sophisticated way it to use stainless tri clamps and endless other stainless parts that could allow pressure fermentation, carbonating, closed transfer, etc... Worry about that later.
Like mentioned, for now you don't need a pump and can gravity transfer your wort into your fermenter. When you upgrade you'll want to have silicone hoses and disconnects.
Above is essentially everything you need to make wort (equipment wise) + 4 lbs of PBW, 32 oz of starsan, hydrometer, etc..
For now, just use smack packs for yeast and you should be good. You can get into making yeast starters later on, and when you do, that will consist of a stir plate, Erlenmeyer flask, dry malt extract, nutrients, etc..
Because you already have a kegerator, I'm going to go out on a limb and assume you have room for another refrigerator right next to it. This could be a free freezer or mini fridge that you plug into a $30 inkbird controller that you tape the temperature probe to the side of your fermenter and use to control your fermentation temperature. This is really what's gonna make your beer taste like beer worth making.
I like to recommend stuff that's bare bones and robust enough to last hundreds of batches based on some of my own experiences as well as recommendations from a professional brewer who got me started. This hobby can get crazy involved and real expensive fast. BTW, you don't even have any ingredients yet, haha. That being said, do your homework think about what direction you want to go. See what fits in your budget now, and go from there.