The potency problem is the one which remains unsolved this day. I mean there is disagreement amongst the different masters of Homeopathy on the issue. Some like Dr. Kent and Dr. Nash were unabashed high potency preachers. On the other hand British homeopaths like Dr. J H Clarke voted for the lower potencies. (I HAVE THE HIGHEST REGARD FOR Dr. Clarke. His works are a treat to read).
My advice is keep a open mind. Decide after observing the case. If the totality of the case matches well with the characteristics of the patient, even high potencies will do good work. But be careful that the patient can take the high potency. If there is continuous aggravation (especially of the mental condition of the patient) antidote it or give the same remedy in low potency. Remember, lower potency of a remedy will antidote the high potency of the same remedy. I recollect I had given Carcinosinum 1 M to a patient. There was frightening aggravation. Now know this well, Carc. has no antidote. I gave Carc. 30 and everything was fine.
Remember, after giving the remedy, monitor the mental state of the patient. If the patient feels better, you have nothing to worry, even if the pathology is worsening. The cure process is under way.
If you are a novice in Homeopathy, start with 6C or 30C. Go after the 200, 1 M and 10 M only after you have read extensively. Ignorance is not bliss in Homeopathy. Read books. Then read more books, is my advise. Don't be lazy. There is no place for laziness in Homeopathy. Use your head. Be original. Always remember what Hahnemann, Boeninghausen, Hering, Kent, Von Lippe, Boger, Nash, Clarke, Bhanja, Grimmer say. They were greats. They knew what they were talking about. Be sceptical about everybody else. But what those greats said; take it as gospel. You will not regret it.
Essential Reading for potency
1. Select Your Dose and Potency by Dr. P.S. RAWAT
2. Introduction to Homeopathic Prescribing by S.M. GUNAVANTE (Lesson 7 - Selection of Potency and Repetition of Dose)
3. The Elements of Homoeopathy (Ch. 16 - The Potency Problem) by P Sankaran.