A practical way to start is with optical design software rather than trying to do everything by hand. In modern lens design, analysis and iteration are typically done in dedicated optical design programs.

A common professional approach is to model a simple existing lens first, then modify it and study how changes affect performance. Professional packages like Zemax and Code V are widely used, but they are generally expensive and aimed at commercial optical design work.

For learning, a more accessible option mentioned is OSLO, which has a free version for Windows with some limitations. It includes sample lens designs, including simple photographic lenses, which makes it useful for studying how a lens schematic is structured and how design variables interact. The software may have a learning curve, but the included examples and user guides are a good starting point.

So, the basic path is:

1. Start with optical design software.
2. Load and study simple example lenses.
3. Adjust lens parameters and evaluate the results.
4. Use the software’s guides/tutorials to learn the workflow.

Beginning with a known simple design is likely the easiest way to build intuition.