at this moment keep accumulating a kind of good altcoin such as ethereum, binance coin and litecoin is the best thing to do
Those aren't bad choices, tho I think ltc is overrated. BNB might be a little of that as well, and there are other coins on the market better than the ones you named. I'd prefer not to give out a personal list of my own picks because I can't stand shilling, but if I was op I would take a look at coinmarketcap.com and see the top 25 to 50 coins. Those are *probably* worth investing in and they have the highest chance of surviving the next few years in my opinion.
Not yet time to buy altcoins.
I'd say it is. Bitcoin just started a nice bull hop, which could lead to bigger gains and if that's true then altcoins are going to be rising along with btc. Not to instigate FOMO, but you don't want to miss out.
