What does it require to be able to list my Native Token in exchanges, so that users of my ecosystem can buy it?
This is a very broad question. In general any centralized exchange (Binance, Coinbase, ...) has strict screening and a process through which the issuers would be required to showcase the viability of the token and their business model. Not an easy task to get your coin listed for sure.
Listing a token on a DEX (decentralized exchange) on the other hand is pretty easy. Uniswap for example allows to trade any token by importing them. However, there needs to be someone that provides liquidity for your token against another token, otherwise it won't be tradeable.
Cardano currently doesn't have any DEX, but there are a few projects in the making that should launch shortly after Alonzo has been released.