And i am not certain that you can invest in radix. You can buy the native stable coin, but why would you buy something that is not going to appreciate in value (1 token is approximately 1 usd)?
Radix when launched will have its own integrated Decentralized EXchange (DEX). So you will be able to purchase as many Radix Tokens at $1 each as you want, using any of several top CMC coins or a select few of the fiat currencies. Granted the Radix native token is designed to be relatively stable, but you can earn additional tokens in 3 ways. The new supply is split 50/50 between account hodlers and nodes providing various services to the main Radix network. The 3rd way is you also earn fees for doing work with your nodes. So as you can see there are incentives to both hodl and run service nodes.