As far as "annuals/biennials", I save everything except carrots, ginger (not a seed), and corn. I don't save every seed every year. For instance, I save watermelon seeds once only and use them for several years combining with purchased seeds. I don't have enough plants to save from and not ready to landrace watermelon between the clay and the bears.
For corn, I cannot grow enough plants to prevent inbreeding depression. When I did attempt cabbages (which never grew...), I was not planning to save seeds. In my garden, these things sort of worked themselves out. If they are too hard to get to maturity to save seeds, unless I am willing to repurchase yearly, I am not going to keep trying.
This also limits the number of varieties for me. Landracing helps a ton. To clarify, I only grow one variety for species of squash, brassicas.
