Fencing can get pretty spendy if you buy a fancy uniform, but for most casual purposes all you really need is a mask, jacket, glove, and foil. That'll protect your important bits and give you something to stab with. Most clubs will have loaners of all of these, but masks and gloves get sweaty, and it can be nice to eventually have your own stuff.

Absolute Fencing is a good company with affordable gear.

• Mask - $100 but it saves your face
• Weapon - $30-50 for a non-electrified practice foil. I learned on a french grip, most people use pistol grip. It's whatever.
• Jacket - like $50-100?. Back zipping ones are cheaper but are kinda annoying if you have long hair.
• Glove - I use a gardening glove I got at home depot or something. I gave the left one to a left-handed fencing buddy. It just needs to be sturdy, and have a pretty long cuff so your sleeve opening isn't exposed.

You don't need the expensive electronic stuff, or special pants or shoes, or chest/underarm protectors. You'll be fine, it doesn't hurt.

For HEMA you can keep the same mask and jacket, but you also need at least a gorget and much more protective gloves. Probably all sorts of other pads based on the sword, but that's what I used for rapier. Also HEMA swords are expensive but also way coler. Whacking people with actual swords is a lot more dangerous than poking them with a bendy stick. HEMA clubs also usually have loaners.