I recommend you stick with the major brands and there are several good ones to choose from. I don't consider Branson to be one of them, not picking on them but they haven't got a big enough footprint in the tractor arena. Kubota, Deere, Massey Ferguson, Mahindra, New Holland, Ford, Case IH all have had tractors and parts available for a number of years. Kioti is another brand that has gained ground in the last few years and seems to be well liked. Yanmar is another brand that has been around for years and can be a good tractor. So there are lots of what most consider to be a popular brand out there. When considering a used tractor you should check to see if you have a local dealer for that brand as that should help with service. It is best to be open minded about brands when shopping used and for the most part not limit yourself right out the gate.
About power I would recommend depending on what you find a deal on about 35 minimum to 60 maximum. Forty pto hp should work well for anything you need to do.
I would go with R1 tires if you need alot of traction but would say that R4 tires would be fine if you go with a rototiller instead of discing. Recognize that a forward rotation tiller actualy pushes the tractor forward in operation. i wouldn't let the difference in the tires choices between R1 and R4 make the difference in choosing a good used tractor.
I prefer the hydro transmissions but have both gear and hydro tractors today. For someone doing a wide variety of jobs I feel the hydro is a better choice. My tractors have the steering brakes on the left and go pedals on the right on the hydros so you can use a brake and a go pedal at the same time. Most gear tractors will have the clutch on the left and brakes on the right and this works well too. I would consider both gear and hydro tractors in searching for a good deal. Again the more you limit your choices the less youhave to pick from. Whatever you do make sure you get one with power steering as that would be far more important imo.
If you think you want a fel for the tractor then buy it now already mounted and included in the sale. Far cheaper than adding on later. I recommend you start checking on line at
www.tractorhouse.com and
Used Farm & Agricultural Equipment - John Deere MachineFinder to familiarize yourself with some of the tractor models and get a rough idea of what prices are. Also read the forums here to get better aquainted in general.