Here are some guide prices for gear bought second hand at sales or off ebay. Also some of my thoughts for your situation.
Chain harrows usually make about £100 -£150
Roller about £800. - I borrow one from a neighbour for peanuts-is this an option ?
Toppers always make £500 plus if they look any good, often they can be over 20 years old, yet as mentioned above you can get a new Fleming (well established British make) at 5ft width for about £700. I would suggest buy new.
If you want to mow lawn areas for a nice cut you need a finishing mower, these are more expensive, but if it saves on buying a ride on you are quids in, can you access most of your lawns on a tractor and do the edges/awkward bits with a normal push mower ? I have recently bought a finishing mower to save work for the ride on, it gives a great finish, but also I have successfully used it as a topper by holding it at a higher level on the hydraulics of the tractor. So possibilities
?
A 3 ton tipping trailer you can get tidy ones for 700-800
So that leaves a tractor, if you don't know what your looking at you really could do with finding a friend who knows what they are looking at. There is detail which you won't fully appreciate at this stage like has it got a pick up hitch, a hydraulic outlet for tipping your trailer, live drive pto and position control hydraulics.
I would suggest if you want to run on your garden an MF 35, ford dexta, international 434 size machine is where you want to be, they will easily do all you have mentioned And are light. A quick add up of the above leaves you with about £2500. This should be achieveable.
All traditional makes are strong well made and long lasting, parts are generally cheap and readily available.
Avoid foreign makes where this wont be the case.
If you buy something bigger than mentioned, make sure it has power steering or it will be a nightmare to manoeuvre in tight spaces.
Hope this helps.