Solely for Ethereum ?aren't you planning in adding other coins ? it is good that you will trust Ethereum because it is one of the safest currency but we also Knew that there is another word about "never Put all Eggs in one basket"
Next bullrun is near to come , so be ready buying every coins that you believe will set you to become another rich person from crypto market.
As you mention, never put all your eggs in one basket and you will have a greater profit when investing in less popular (or smaller altcoins). On the other hand, investing in ETH is a much safer bet so it all depends on how much risk you want to take.