What’s best depends a lot on where you are going to use it and how.
If you are planning on running track power outdoors in all but dry climates, Stainless is a good choice. I am in New England and have had stainless outdoors for over 5 years. I use the standard Aristo screw joiners except I changed the screws to larger head Phillips screws. At switches and a few other places I use Split-Jaw rail clamps. I have had no power problems to speak of and the track only requires wiping with a soft cloth to clean. The negatives of stainless is that it looks terrible unless painted; it’s the most expensive track, and it’s harder to bend and cut (but not too hard).
I am slowly converting to battery power. Since you presently only have one loco, starting with battery power can save you a lot of money on track and power supplies plus saving lots of time and effort because no wiring is needed. For battery power you can select cheap aluminum rail - or even make your own with wood 
If looks are your primary concern, then select a rail that is smaller than the common code 332. Code 250 Nickle Silver will give most of the advantages of stainless in a smaller profile.
Brass is tried and true. It conducts electricity well but needs constant cleaning in most climates for track power. If you are going to start with a small loop the maintenance of brass may be worth the cost savings over stainless. In my opinion the Aristo & USA brass is way too yellow and never really darkens up. Older LGB rail will darken with age and look quite good. Piko says their brass formula is the same as the old LGB, but be careful of their non-standard geometry.
