What remedy potency should I take?

Take 6X if at all possible. If 6X is unavailable take the next lowest remedy available. Here is why.

Remedies vary greatly in strength. When you purchase a remedy it will have a number and a letter to indicate it's strength. For example Arsenicum Album 30x.

X = 10
C = 100
M = 1000

Never take anything over 30c without the recommendation of a licensed homeopath. Even 30c is a very high potency remedy and I do not recommend it until you have gained experience working with homeopathy.

In general anything under 10X will work at the physical acute level and this is definitely what I recommend to begin with. Most remedies are available in 6X potency.

10X-30X and anything up to 20C is going to work on multiple levels at once but it's primary action is on the mental level and it works secondarily on the physical level. Anything higher will work on the spiritual level as well as the mental and physical levels. When I refer to the spiritual level I mean on a fundamental level affecting ones outlook on life in addition to ones more immediate mental state.

This can also be thought of in terms of what part of the body a remedy works on. The lower potency will work on more external and visible symptoms. Where as a higher potency remedy will work closer to the core of your being.