For hanging baskets I use trailing geraniums, they don’t mind if you miss a day or three of watering. I like white ones, but the very dark red are lovely too.
For borders look for reliable perennials , that means they come up every year. I like cranesbill geraniums, lots of different colours/ leaves, penstemon, campanula, salvia , sedum,Siberian iris,geum, crocosmia, ladies mantle, hellebore, rudbeckia, .All easy to get hold of, don’t require much looking after, pretty reliable in most soils. After a few years you can usually divide the plants to make new free plants or share with friends.
I also like reliable things that will happily seed themselves around like cyclamen, acqualegia, (spelling) bronze fennel, California poppies, Nigella, field poppies, marigolds, Italian arum ( bit of a thug). They might take a bit of establishing but once they get going they will keep coming if you see what I mean..
Bulbs such as amaryllis, nerine are a bit harder to get going but lovely, so start yourself off with spring flowering bulbs, the usual suspects.
easy annuals like nasturtiums and morning glory are satisfying to grow. Herbs are pretty and do well in pots usually.