I learned about the gels as I got older and heavier (6'1", 250 lbs) to prevent my feet from hurting. Keeping the inside of the shoe clean and being able to wash or change out the gel is merely a bonus.
I agree with not wearing the same shoes everyday. I have over a dozen Sperry's in different styles and colors that I alternate with. Some I have had for years that still look new inside and out. Of course that was mainly due to only wearing them a few times a month, not more than once or twice a week anyway.
Many people try to tie them in the typical tennis shoe fashion. I initially tie them the way leather laces should be tied to prevent them from coming untied while making them easy to kick off and step into. A sore back will appreciate that! And it is a better looking knot giving a symmetrical look, in comparison, it's like the typical neck tie knot verse a Windsor. I don't like cockeyed! LOL
The stores will try to convince you that you can only use leather cleaner. Perhaps on some types. As I previously mentioned, I throw them in the washer and stuff with newspaper to dry, with no ill affects. (Stuffing with newspaper keeps them from shrinking or loosing their shape. Although I will say in my youth, nothing would make a new pair of leather cowboy boots fit like getting them soaking wet and wearing them until dry. Fit like a glove!
If you like flip flops, try on a pair of Reefs. Not the cheapest as a good pair that will last is going to start at about $50-60, however they will last years. The cushion of the cheaper $30 ones will break down much sooner, so don't try to cheap out as your feet are what carries you and when they hurt, you're not having a good time!