Problem with My Fruit Sage

I bought a plant of Fruit Sage from Richters a couple of weeks ago. It's grown in an 8-inch clay pot without drainage hole. I have no experience in growing Fruit Sage. I only learnt from the plant tag that it needs good light to grow and is tender. I also learnt from one of your past Q&A that it does need a lot of water too.
At first I placed it in my kitchen which has south facing windows so that the plant can get a lot of sun light. A few leaves from the bottom of the plant turned brown (started from the tips) and dried out. I figured out that my kitchen could be too warm for the plant so I moved it to my living room. My living room has really huge north and east facing windows. It is quite bright even though both windows are dressed with sheers. Now some leaves of the plant started to dry out, not turning brown from the tips this time but the whole surface of the leaves is drying. The leaves are losing their softness and turning paper-like. Can you help me to save my plant?
Also how can I tell whether my fruit sage is getting enough or too much water if my pot does not have a drainage hole?

It looks like the roots of your plant are in trouble. I think it would be better if you were to find a plastic pot that fits into the pot without a drainage hole and replant the fruit sage into it. You can then water the plant by removing it from the overpot and replacing it in it when it has finished draining.
You can get an idea of how wet the soil is by poking your finger into the soil surface. If it is moist things are fine. If it is squishy wet, turn the pot onto its side for about an hour to allow the excess water to drain out. If it is dry, water in a hurry! Pots with no drainage accumulate salts - quite rapidly if your water is hard and even faster if it is chemically softened. These salts kill the roots and with dead roots the plant dries out no matter how much you water.
The bottom leaves of the plant will die if your conditions are quite different from those in the greenhouses it came from. You have cause for alarm only if the new leaves are dying too.
You might want to place the plant into a slightly closed clean plastic bag until the roots seem to be doing their job properly. At that point, gradually remove the plastic bag over a period of about a week.