Summer time is here and I want to self-study to get ahead in a bunch of subjects. How can I start to break this down into a regular thing? My normal study habits are awful and outside cramming I've hardly ever done it

I was thinking I should start light and build up from 1 hour with pomodoro method. Where should my end goal be for studying? Will I hit diminishing returns if I'm studying multiple subjects? Tips?

So far what I want to learn atm if it helps:
>Calculus up to calc3/multivariable level
>Physics which is low level and will involve a lot of mechanics, work, thermo equation shit
>OCHEM
>A path through engineering which I'm not sure on topics
>Software development through programming and algorithms