Grin is a new coin and I have heard a lot about it. Bitcointalk forum admin has started to accept grin as a payment method. Is it worthy to invest in grin now? The current price is $4.50 or something like that. What do you think? Will it increase or decrease more?
Judging on it's price history -
https://coinmarketcap.com/currencies/grin/, I can tell that you are in the right timing to buy this coin.
I know you believe on this coin, you are just asking about the timing, so that's my opinion based on it's price history only.
I don't own this coin in my portfolio as I like old coins and I don't have extra funds now to buy new coins.