Firstly it is not shares market if I understand that you are talking about crypto market i.e. coins, many ICOs are listed on
coinschedule website that is running, ended or upcoming, with their token sale date also links to their website, white paper & team members. From
icorating you can check specific ICO rating & risk score.
Regarding which coin will be valuable in future, no one can predict it solely depends on their strong team the product they are offering & other factors too. You have to do your own research to invest in crypto project read their white paper to get understand about their project.
To invest you have to visit their official website and follow the guidelines, most ICO only accepts Bitcoin & Ethereum only some also accept payment via credit card.
But if you are talking about to buy Bitcoin, there are many websites out there check below thread.
https://bitcointalk.org/index.php?topic=3158489.msg32829387#msg32829387