ye shrimps would be cheap. you can buy tank for breeding shrimp , so it will be a good idea. it how big my weather loach is at the time and how thick he is too , at the monment he is 10cm last time a measure him, when a get my tank he might be 12cm to 20cm you never know, it says on the internet you should have tankmate when the oscar is young.
iam think of buying a second hand fish tank with hood and ligths and get a new stand a filter , heater ....... so it will be cheaper!!! and i could get it sooner
i see some oscars for sale in pets at home , they were about 3cm to 5cm , they had about 6 of then all different kinds and they cost £5