I like to buy some tokens/coins for little amounts of $5 or $10.
Is that possible?
You should sign up on an exchange for this. All exchanges have minimum buying and selling amounts for every coin. It is determined by the exchange and you cannot negotiate about it. But yes 5$ seems like a decent amount to buy some penny altcoins and small volumes of bigger altcoins. But make sure you do proper research and analysis of the coin before you do so.
What to do and where to buy?
There are so many exchanges to choose from. Poloniex, Bittrex, Binance and so on.
Is there any exchange where i can buy through paypal especially doge coin.
You cannot buy doge with paypal. Heck you should not buy/sell crypto with paypal. Deposit on exchanges and buy using that. Then withdraw to doge wallet.