All this advice is in my opinion sooo mediocre. Yes BTC ETH LTC a such are safe bets, but that's not the thing to do in this market. The market is a very young one and has astronomical upside in the next 15 years.
But talking in a lower time frame(1-2years), for ETH LTC and other such Top 10-20 coins to gain a 10x gain is needed a real Alt cycle or a BTC run. In such conditions "all ships rise" meaning (the important thing in that situation) that small caps will rise too. And hopefully, we all know small caps go faster than high caps.
I would play it (and i do) with good small caps and wait for the next cycle(which could be now (Altcoins)) to accumulate (ofc) BTC because he is and will be the king. Why not increase your BTC holdings within the altseason and wait for the btc run with 5x-30x BTC you could have bought now.
(To do that you have to choose good coins, have a strategy*, discipline on 100%, and NOT give in to your emotions) ( *The strategy is to watch the market closely and bring yourself in a position where you can anticipate runs and flip that profit into coins that haven't run yet but have a high chance of doing so**) (**For that you need to know TA, FA, your risk level, overall state of market and hype about that coins/coins).
Coins i would recommend are LUX PHR MSP PIRl BIS PRL SCT MWAT TOMO HKN ACAT PBL POLY TEL TFD ELA ZINC XSN SKY LINDA DBIX ZER XPTX MAN SPHTX ACAT XDNA and such. Yes, I hold some of them and i hold them because i believe in them and that's why i write them here. Some did already pump, some have, it's up to your risk level and TA to choose to buy them or not.
Safe and smart trading!