I would say to invest your money only in one basket is a bad idea unless you have true beliefs of that coin or the project.

If it was a month ago I would have told you to buy Ethereum, but currently ethereum is counted as high, but in crypto the sky is the limit so you can never know when it can hit the ATH, but I know another coin you maybe should look into currently I'm into privacy coins like xvg , monero and stuff like that
but best of them all would be deeponion currently it's on a dip whales holding it back down so they can buy more , and each mid of the week it pumps up look at the last 7 days chart you will get what I mean, in this coin you can even join their airdrop they have another 14 drops , check it out, I'm out.