I made jumps from treated posts and bought pvc round "rails" from a home improvement store. I have some that are 8', 10' and 12'. I put stripes on them with contact paper. I also have some blue plastic 55 gal drums since those are a common jump you see in eventing. I ride and jump in my pasture, on grass, but that is what I jumped on in the cross country portion of eventing. I am on clay and what I have to do is drag a disc harrow sometimes to level out hoofprints that get made in the winter or whenever the ground is wet. Since that is also my pasture I can't use anything that will rip all the grass out, too. I have a small disc that I can weight down that will do it with several passes. My neighbor has one with hydraulics that works quite a bit faster and he just does it lightly. Neither of us has a sand arena but I am wondering how a landscape rake would work on that as opposed to an arena drag, which is considerably more expensive?
Are you in a farming area where you can spread manure in fields when they aren't in use for crops? If so it is possible you will be storing manure for long periods of time also. The farmers will give you permission to spread, anything that can help fertilize their crops they will gladly take.
I use my loader everyday for mucking, but if you won't be it may not be necessary. Some people just put the spreader on their tractor and park it in the barn aisle and dump their muck tubs right into it. Since I can't always spread that wouldn't be the best set up for me. Not only that, but I don't want that manure pile too close to the barn so I used to carry those tubs a good long way. Now that I have the tractor I built a giant 3 sided compost bin in my back yard to put it in when I can't spread. It is easy to get to with the tractor, not too close to the barn and is convenient for loading the spreader and getting that into the field when it's empty. Mowing with a loader takes some practice but I just back into corners to get that grass mowed. Mine is not quick attach.
As for post pounders, I have no experience with them myself, but a friend used to work for Ramm fence and I know they use them on fencing they install. I could ask them about what size tractor they are using. I actually dug most of my post holes by hand but I was young (and kind of poor) then. A PHD on a tractor seems to work fine here and my soil is kind of rocky, mostly limestone. Sometimes I hit one and have to dislodge it and pull it out. I also sometimes hit old, clay drainage tile.
I think to advise you best, we will need to know all the uses you want from a tractor. Mine had to be a multi-use machine: stalls, mowing, driveway leveling, post hole digger, bale stacker. If I buy that second tractor for the spreader it will likely be an old, and cheap tractor. I have a friend with an old Farmall he doesn't really want who is willing to sell it to me with the implements for $1000. I don't need most of the implements he has and would sell those, which gets me a super cheap tractor for pulling the spreader. So there is that possibility for you also. Maybe one tractor small enough to do barn chores and a bigger one that could do other things?