There really is no secret method out there. Sure there are some very small alt coins which you can mine however there is no guarantee that they will do an 100x. And the daily profitability of those coins is slightly less than mining ETH directly.
If some new coin and algo comes out then as soon as it’s listed on one of those “ whattomine” website and it shows as slightly profitable than ETH you will see the difficulty sky rocket because everybody wants a piece of the more profitable pie.
Mining is extremely difficult these days. More difficult than in any of the previous cycles.
There are coins that can be mined easily on your normal gadgets (laptop, mobile etc) but its only till the time they don't have any value or are not listed on any exchnage. Rest as coins goes on exchnage, many others join in and complexity of the coins goes up and you need specialized hardware to mine it.
I do agree with you that its more profitable to purchase coin directly rather then mining it.