Having just been where you are, I think the biggest bang for your buck is with a PTO driven roller pump and a 3pt hitch 55 gallon sprayer. Yes, you have to be a little careful with maintenance -- a few drops of oil or antifreeze in the pump after use -- but you bought that tractor for its PTO (among other things) and you might as well use it. You'll want at least 55 gallons, if you are planning on working on 5 acres. Anything less and you'll be filling more than is necessary. I rented a 25 gallon electric, then bought a 55 gallon PTO and am very happy with it.
If you have a bit of the "do-it-yourselfer" in you, you can save a bunch of money by buying a used drum, buying some plumbing parts, and using a little ingenuity. I DIDN'T do this, because I got the idea about 2 days too late, here on TBN. I did rig a 55 gallon drum to use my roller pump to carry water to remote new plants. It would have been just a few more parts to build a boom. I set up my water tank on a carry-all, where a boom could be added easily.
Whether you go with a home built rig or a ready-made - I vote for a roller pump rig that adds versatility and power to your spraying needs.