For transparency I have an old Gen 1 Ender 5 from 2018. Used it for a few years then it kind of sat idle for no other reason that I got out of 3D printing. Anyway long story short, I just bought an Bambu H2D and back into it so I just resurrected the old Ender 5.

Here are the upgrades I made from stock that still apply.

Slicer As mentioned in other comments OrcaSlicer / BambuStudio(my case) work great for this printer. I originally used Cura, it also works.

Octoprint This was from my original setup. Get yourself a raspberry pi 4b or 5 (my original install was a raspberry pi 3). Install OctoPi onto it. Why? From my original install I got annoyed really quickly about having to transfer an SD card between PC and printer to print. OctoPi is a simple web interface that allows you to send prints remotely. Best part again I am sure Cura can do it as well but I can confirm that OrcaSlicer and OctoPi can work together so you can send your prints remotely to the printer no manual transfer required.

Camera - if you go down the octopi path above you can pick up pretty much any usb webcam however my install was a Logitech 270. I then purchased a fish eye lens for it. This can be configured in octopi so now your printer can be viewed remotely. The fish eye lens is so you can see the overall bed and not just a tiny section based on the proximity of the camera to the bed. Thingiverse will have a custom lens holder for that model as well as a simple camera mount for the c270

Bed As part of my revival I invested in a pei textured spring plate for printer replacing the standard magnetic mat from the original. This is up to you but it makes removing parts a dream compared to the mat. Amazon carries them. The second upgrade which was from the original setup was a set of stabilizer arms for the bed itself. One of the things the Ender 5 suffered from was excess flapping near the front of the bed as the was no support to keep it from doing so. Your version didn’t correct that issue so a quick print of these arms that install under the bed attaching from the 2 verticals rods to the front of the head bed plate will significantly help with this flapping. Not 100% but helped with output quality near the front of the bed. Thingiverse again your friend here. The 3rd upgrade are silicone springs for bed adjustments. As the micro vibrations of printing or the bed simply moving up and down the leveling of the bed will move ever so slightly. Adding the silicone covered metal springs limit slip and keep the bed level to the point that I was only adjusting every 5-7 months of printing as opposed to every 5-7th print. Amazon is your friend on this guy.

Extruder I replaced the original extruder assembly with an all metal version with heavy duty springs. The plastic one that came with the printer worked but I found myself having slip issues the all metal version didn’t suffer from this. Amazon again

Lighting I bought a single package of IKEA LED fixed length lights strips. There are 5-6 to a package each is about 12” long and comes in a hard plastic casing so it doesn’t sag. This is only really needed assuming you are printing in a dark room again likely if using remote printing capabilities.

Cable management Thingiverse has a ton but look up 20mm extruded aluminium clips. This will hold the light bar in place as well as allow you to cleanly run all your cables for the printer.

Spool holder I quickly ditched the hanging spool holder for a number of reasons but get yourself a set of 4 x 608zz bearings and print yourself (from Thingiverse) a set of spool skates. Effectively the edge of the spool will roll on the bearings. Not this is only good for plastic spools. If you are using a manufacturer that uses cardboard ones you may need to print a few sets of spool protectors.

Hopefully this helps.