Internal drives external connection

have you guys any experience or recommendations on how to use all your old drives.

Thing is. I switched cases and didn't bother to install my blu-ray drive but still want to watch a dvd movie now and then and sometimes have to burn a cd for University.
Also I want to take out my HDD and just use SSDs in my machine.

But I still need a lot of data that is still on my HDD. Of course I could buy a new external HDD but there must be a cheaper solution.

You could just get a hard drive dock

I have some cheap usb metal case thing for an old laptop hdd, I don't like the fact there's no power switch on it, tends to get hot, fine for occasional use but no good plugged into the tv or router

I use a simple USB to IDE/SATA converter cable that hooks up to USB2, there are USB3<->SATA converters now that should be fine, you may need a power brick of some sort to go along with that if it is a non-laptop old device you're using though (due to power use).

Alternatively, use a SATA -> eSATA setup in your new case, and hook up your old drive that way. Not sure what the most compact & not insanely expensive option would be, but you could even decide to hang a power cable & SATA lead out of the back of your new setup and just throw the blueray drive on top of your case on top of a rubber mat or something to 1) avoid is sliding around and 2) reduce vibration :)

I use an Akasa USB 3 DuoDock you can add in a simple HBA card if you don't have USB 3 in the system.

Alternatively my HAF XB EVO case has two hot swap Sata 3 drive bays which are just as quick to stick a HDD in while the OS is running.