1. STOCK MARKET. Invest in the stock market measure your risk. Nowadays its so much easier to invest in the stock market there are plenty of platforms like Sofi, Robinhood, Public, Fidelity, Moomo, and much more that offer fractional investment where it can invest any amount of money.
2. INVEST ON CRYPTO MONEY. You can directly from different sources like Sofi, coinbase, and store in digital wallets. Also you can mine all kind of crypto money from the most little ones to the most popular. You can even start on an android phone or a computer or GPU.
3. MINING CRYPTO. Verus coin is a proven crypto that can be mined on old android phones. All that is needed is verus box app and the miner. Bitcoin can be mined on android on Cryptotab browser , Cryptotab farm without using much cpu.