Well Personally I like BMX Bikes as for they are cheap and everybody's size.
Road bikes are more expensive but you can buy them used on random websites (Amazon, Ebay, Craigslist)
Mountain bikes are Some times cheap but From my Experience, are the worst bikes
I bought a new bike today and i had a 300$ limit too And i looked on google; Bikes stores near ________ (City) And bought a new BMX Bike for 280$, New Biking Gloves For 25$, And A new Bike Lock for 13$.