Actually, dividing and conquering is your best bet when it comes to tackling science.
First, let's break science into its branches. I am aware that science has biology, chemistry, physics, geology, astronomy, and math as its primary branches. Each branch has subjects within it: biology has within it medicine, taxonomy, ecology, and cellular function within it. Chemistry is broken down to inorganic, organic, and electrical (the voltaic potential). Physics is broken down to motion (kenetics), waves, optics, and thermodynamics. Of course, there may well be other divisions.
And then there is the integration between branches. If you take one branch and learn it out of context, it will be much harder than if you start with the entry level and try and find common denominators. Better, for instance, to start learning the elementary facts about a major branch (like biology or physics). Once you learn the basics, it will be that much easier to learn more specialized features of your branch. The broader a basic knowledge you have (and the better you are at integrating one concept with others), the easier it will be.
After you have selected one branch, you dedicate a unit toward that. You do online research. You may need to take courses in that branch, but it will probably cost you money if you do. Master the basics. Then, try to integrate it into the sub-branches so it will be easier to learn. Once you have the desired level of proficiency in one branch, you move to another. Repeat this process until you are satisfied, all the while trying to integrate one branch with others. Math is most important to integrate with science--it will make learning those formulas that much easier.