Size your batteries
Your first task is battery sizing. First you need to get conversant at volts, amps, watts, and conversion losses. (which are to be avoided). So you can go "Ok, 60 watt laptop, that means 5 amps at 12V, minus the 20% inverter losses" etc.
Then you can get to watt-hours and amp-hours, which are units of capacity.
Then you can figure out how many watt-hours or amp-hours you need for your application.
Now, you must derate your batteries or you will quickly destroy them. With a lead-acid battery you should plan to use only 30% of its capacity. (i.e. 70% of its capacity is in reserve, and rarely used). With lithium it's reversed, you can pull them down pretty low. That makes a "watt-hour" of lithium worth a lot more than a watt-hour of lead-acid. (it is also a lot more expensive).
Stupidity during battery sizing will result in a poorly performing system that will be very frustrating and probably result in abandoning the project.
Size your panel
Now you look at how to recharge the batteries on a regular basis. It helps to talk to solar power people about local data, but you should be prepared for your system to bridge across days of poor recharge rate. (which is kinda back into "battery sizing").
You need a solar panel that's big enough to charge halfway well on cloudy days, and charge fully in decent winter days.
During summer sunny days you will probably have a glut of solar power that you will not be able to fully use. If you size the panels to only adequately recharge during ideal times, then it will under-perform the rest of the time. However making that mistake is fixable by adding more panels.
Designing a solar system is not kid-stuff. You can't just throw a bunch of random parts at it and expect a successful project that serves you well. You have to learn, plan and think. This should be the tip of the iceberg in your research. When you do, it's money well-spent.
