Unlike most suggestions here, I bought almost all my implements when I bought the tractor. Why? Because I got 0% interest for 5 years, and I knew I would rather roll it all into that than try to come up with $500 here and $2000 there later on.
I got a 1025r TLB with a PHD, a rotary cutter, a tiller, a rear blade, and a box blade. I later added a boom pole and a quick hitch. The only one I haven't gotten use from has been the rear blade, which I got for clearing snow off the driveway. And I haven't been there when it was snowing yet. But I bought them all with specific uses in mind and needed them all. Figure out what you need to do and buy the tool to do it.
Re the PHD in clay soil, I have clay soil and it does a decent job when it works. Sometimes it can be an exercise in frustration. My advice, buy plenty of shear bolts. 😄 Also, in my area, it works well in all seasons but summer. When that clay is dried and hard it's like trying to drill into ceramics! It will still work, but it takes way more time and effort!
I am thinking a post hole attachment for the needed fence. That being said, how do these tractors do handling it? It’s clay but no roots or rocks.