Well, as a long time caster,, I can say I enjoy it, as it provides me with an extra way of custom making my own ammo.
As noted,, the cast boolit forum has a wealth of info.
You can buy new stuff easily, and not invest a huge amount unless you want the "better" brands with a few nicer features.
But you can also be a "frugal" caster & start by shopping for good used stuff. Local auctions, pawn shops, WTB ads in places, etc can get you the basics.
You can get the basics,, (casting furnace, mold(s), & make a few tools & go at it. You'd need a good hardwood mallet for knocking the sprues, and a good pair of leather gloves & safety glasses.
Once you find the alloy (metal) you need,, you'll need a sizer to match your gun bore diameter. You can get a Lee push through sizer,, or invest in a bench lube/sizer unit. You will need different diameter sizing dies too.
One thing that has happened over the last several years is the use of powder coating vs using a wax/grease lube. Most of us who cast are now powder coating INSTEAD of lubing.
It too is easy,, and can be a very small investment.
A Goodwill cheap toaster over, quality powdered paint, A plastic container to put bullets & powder in & shake them. A cheap plastic colander, plastic tub to catch excess paint & you can powder coat.
Now,, if you decide to get SERIOUS & make bullets with plans to use them for serious work, (hunting big game,) then top quality molds, and proper alloy will get you there. I've pretty much quit using any of my Lee molds. I mostly use MP Molds. I have found that their design, as well as their quality is among the absolute best out there.
Basically, there is a LOT of information out there,, and it will take some studying. BUT it can also be fairly easy, and you will learn what YOU need to meet YOUR desires.