if you know what exam board your economics a level would be, i suggest getting the textbook designed by that board. i currently use the AQA one and it is extremely useful
but a lot of the syllabuses from each board are quite similar, and when it comes to economics, it'll never hurt with knowing any extra stuff - it'll be great to put in any essays!
i must say though that in general, at least at our college, we are discouraged from using one specific textbook. this is because textbooks can be confusing but also many lack the detail and breadth required to give a true insight into economic topics, although don't worry, there really isn't too much content in this subject - just a lot of general reading you could always be doing.
hence, i'd recommend using online resources too! there's some brilliant youtube videos, people such as econplusdal, which are really easy and simple to follow through with and can make studying economics a bit more exciting. also, magazines for economics targeted at A-level students are simply amazing. i learnt more from them than i have from textbooks, simply because they not only explain the relevant economic theory but link this to current events in a way us teens would actually understand. these magazines also have questions in them and model answers, as well as extension tasks, which is absolutely great for getting you started within this topic and maintaining your interest.
good luck with econ!