In-dapp altcoin purchase

[S_Sergievsky]

Hello!

We are working on the concept of a decentralized mobile application, where users can purchase virtual goods. The value of these goods is linked to fiats (for example, $1), but you can purchse these products for special app tokens only, which you have to purchase with fiats first. The value of the tokens is determined by the exchange rate at the time of purchase.

Need your advice here:
How can you arrange in-app token sales directly from a token exchange?