Based on the existing answers and question, it is best to save your Klay tokens in the Kaikas wallet. The Kaikas wallet is the official wallet for Klay and can be downloaded through the link provided in answer 12. It is the most secure way to store your Klay tokens and you can also trade with it. Additionally, you can explore the various exchanges that list $Klay for futures trading. However, it is important to do your own research (DYOR) before investing in any exchange.