I do lots of different things guided by whatever inspires me at that moment, but I often lean towards I Ching and Tarot. I Ching is what I would usually recommend someone learn when they are first starting out, it's very simple to do and the interpretations are very clear. With Tarot there's a little more of a learning/experience curve before you can reliably interpret your given spread, but it also allows for more complexity. I Ching is very good at telling you the current state of things, exactly what's going on right now and how that can affect your potential outcomes. Tarot is very good at telling you what might happen along the way following certain choices. These systems work well alone or in combination with one another, as do most others. It's best, imo, to choose the system you feel most drawn to and work with it constantly until you feel very comfortable with it, then continue trying more out. You may find I Ching's restrictions appealing in practice coming from a background with astrology, or you may find that you prefer something more free to interpretation like runes.