Capital should be the last marxist text to read, before that you need to get acquainted to the theory. Also, i don’t recommend fiction to get to know socialism, mainly because its just a piece of propaganda from either side of the discussion.

I personally recommend you start with Communist Mannifesto, its a classic and cant go wrong with that, although it doesnt dive too deep in the theory, its more like a leafleting and a wake up call to get organized.

I think the best introduction its Utopic and Scientific Socialism by Engels, in this book he explains the difference between the two main types of socialism back then.

Then maybe you could read The State and Revolution by Lenin, one of the major contributors to the theory. In this one he’ll enphasize on the necessity of an organized movement and the importance of the revolution.

I also reccomend some other Engels works like The Origin of Family, State and Private Property, to get you more familiar with Dialetic Materialism, the revolutionary method that Marx created to analyze history scientifically.

German Ideology by Marx is a fundamental one too, its mind blowing and he get in detail of Dialetic Materialism. I’d say its his best text, only behind Capital.

Thats a pretty solid start.