BAPaul
The shirt may have been a factor, if it was official that is. Majority of people here buy them from the market and unless it has the Adidas 4 strips, an wonky shaped badge sown and is made from 100% of the finest vietnamese polyester you`ll stand out like a sore thumb in a football shirt.
My tip is to keep your head down and ignore them, never give or buy anything as others will see you and harrass you. Just say a pleasant no, gracias under your breath. It`ll obscure your accent. Its exactly what the locals do, if you start giving them things or trying to converse they know your a foreigner straight away.
p.s
Also, as someone who has done a few years of learning Spanish via skype. I`d say try and get a local one to one teacher rather than remote learning. Skype learning is great if there is no other means, but it does feel detached and any connection problems cause delays or drops in the speech and you sometimes end up talking over the top of each other or missing words. I now have a one to one teacher and it feels much more natural to communicate with. Thats my opinion anyway.