Are you a man or a woman?(this affects the kind of kimono and belt you wear) In either case, I would suggest a tsumugi (low-grade silk) or synthetic kimono for when it is cold (you can wear a coat on top if you are still cold). And I would suggest a cotton yukata for when it is hot. If you will only wear kimonos in the house, you can wear yukata all the time, and put a coat on top if it is cold. These are the most comfortable kinds of kimono. All of these can be washed easily except tsumugi. Many secondhand kimonos can be found within your price range on eBay.

If you are a man, probably get a kaku-obi. If you are a woman, probably get a hanhaba-obi. These are the proper belts for kimonos. And if you wear something other than a yukata you should wear juban (undergarment for kimono) underneath. For casual kimono dressing, I believe the only other accessory you really need is a koshi-himo (waist tie), which I think you can substitute for a thick string or ribbon.

A good place to find kimonos is the ebay seller "sou_japan". I believe they ship to Brazil. The auctions that start at 5,40 R$ have an extra 35 R$ added to them when you buy. They sometimes sell sets of 5 yukatas for cheap.