forget about "good flat 1 bedroom around 3500-4500q with pool & gym in the building." for such flat you will need to pay QR7000. For QR 3500 you will be lucky to get 1 room in 2-3 bedroom flat of your description. For QR 1500 a month you can get an avarege car, like Nissan Tiida, or Honda City or maximum Ciic, nothing really fancy
Welcome to Doha!