The cheapest fees you will find on CEX platforms, but without knowing your country, the method of purchase, and the amount of DCA, you will not get an accurate answer (fees play a major role in profits.)
He can check different fees on many centralized exchanges with
https://www.cryptowisser.com/exchanges/Note that the DCA strategy is a long-term strategy, but its results are good in a bear market and waiting for more than 3 years. However, if your strategy is for a year from now, you may incur losses.
DCA is surely a strategy for long term, not short term.
The DCA website
https://costavg.com/ with exchange fee % from Coinbase, Kraken and Binance can be a good reference, but he can set a customized % in fee too.