How much could I get for this pc?

Used computer is worth $100

Used 24" display (if in perfect condition) is worth $75

speakers, mouse and keyboard are included with computer

People like to greatly over-estimate the value of their used hardware.  But if someone offered you $200 for the whole lot, that would be more than fair.

You should list it for $300USD and expect people to haggle you down to a lower price like $260. Though you should give them reasoning why you think it's worth $300 (for example: It can play fortnite at 1080p etc.)

You may have better luck stripping the components and selling them individually.

Few people would buy a second-hand pre-built PC and those that do would not want a processor that dated.

I think you can probably get $100-$200 if you sell the parts. Best case scenario is find someone looking to replace a part on their old machine.

If you can afford it, I highly recommend giving it away to someone who may not be able to afford a PC.

I'll give you £20.00 (Twenty Great British pounds) if YOU pay Package and Posting.

take any amount over $50.  that cpu is over a decade old, as is the gpu