If you are JUST starting out, you should read books that talk about philosophy merely as an institution. Something that looks at it broadly as the history of human thought. The reason I say this is because I’ve found it’s really helpful to have some sort of skeleton in place that you can add meat to– an understanding of the broad movements in philosophy. Otherwise, it’s almost like reading the dictionary. Nothing you read has any context. It just becomes this flurry of random facts that you don’t care about. The trick is CARING about what you’re trying to learn. A couple examples of books like this are:
A Brief History of Thought by Luc Ferry
The Consolations of Philosophy by Alain de Botton
Once you have a general idea and want to start tackling specific topics that interest you, my advice would be to try reading modern authors who have written contemporary books about these older thinkers. Reason being: for every philosopher out there, some desperate ex-philosophy student on welfare has built a career out of knowing practically everything there is to know about them. These people throughout their entire lives have largely done the leg work that I referenced before, and they can be an enormous help when it comes to avoiding misunderstandings and knowing which ideas were important.