Get a good book. Asking for advice is all very well but if you really are a novice you need to read as much as you can.
There are no short cuts to a good garden. Make a start and build on that.
Alan Titchmarsh has some good gardening books for novices.
The main room in your house...
Labour Brings in excellent Renter's Rights - long overdue.





and the other just grass! I can ask further along though.