Newbie here and I want to start trading soon. Just want to get tips on when to invest on btc and eth. thanks in advance!

Before you start trading, please read some book and join group with trading as their topic. Isn't wise to trade without knowledge? know the risk first. Tips is just find buy area and sell it when the price enter the sell area. You can find this area with an indicator like MACD, stockhastic oscillator, or just using trend line. Do that with demo account to find your best strategy and keeep patience. Good luck.
Sincere pieces of advice, though. I will suggest him the same. He should study crypto trading deeply before jumping into crypto market. He should learn when to buy a coin and when to let it go. Practicing the trading on the demo accounts is worthy. They will give him experience without any risk.