When I use ginger, I cut two or three slices, fairly thin(little less than 1/4 inch). It definitely can overpower the spices if you use too much, just experiment. Many people grate the ginger AND peel it, but I don't since its strength increases (More surface area!) plus when you strain it, it can get directly into your cup... I leave the peel, due to lazyness and to weaken the ginger. Make sure your other spices are fresh too.
When you simmer(i use between 3-4 on my electric stove) everything together, alter the amount of tea you use. You usually need more, since the tea doesn't release its flavor as easily at this lower temp. I add the sugar in early if I plan on using a lot of it, then its totally dissolved in the tea and evenly distributed as well.
This method takes too long though, so i usually do it this lazy way now: In a sauce pan, I put my spices in around a little less than 1.5 cups of water, get it to a rolling boil, then turn it down to a simmer for 5-9 mins usually 7 though, Then I add about 1 cup of half and half. Get it to a rolling boil(don't let it boil over like me!, creates a mess...), then take it off the heat (or turn it down to lo to retain heat) and add the tea leaves. About one teaspoon per cup then one heaping teaspoon and let it steep from 3-5 mins covered. Strain, and add sugar whenever. Not as creamy but good. I also attempt to make it frothier and thicker by pouring between two cups at a large height, it helps dissolve sugar too(like chaiwallahs hehe).
Also you don't necessarily need to use half and half; whole milk, condensed milk, and for the sugar fanatics sweetened condensed(almost tooo sweet though) works. The consistency changes, but generally I stick with half and half.
I have used natural cane sugar, turbinado, honey, regular white sugar, and organic natural sugar. Turbinado is the best to me. I really disliked honey in my chai the few times I have tried (it is good with other teas though).
When I have time, I like to get the chai smooth and creamy, yet strong.