You can compose +1 items in Market at WuxingOven (193, 211)
For a +2 item you need 3x +1`s
For a +3 item you need 2x +2`s
For a +4 item you need 2x +3`s
For a +5 item you need 2x +4`s
For a +6 item you need 2x +5`s
For a +7 item you need 2x +6`s
For a +8 item you need 2x +7`s
For a +9 item you need 2x +8`s
You can only compose items of same type (bows with bows, rings with rings, 1h weps with 1h weps and so on)
How to compose +1 items
Re: How to compose +1 items
This should make pricing anything above +1 easier knowing the price for a +1 and then just multiplying it by the number of +1's required for that item higher than +1. Atleast helps myself out. If the maths are wrong, please do tell so I will edit the post. 
+2 = 3 +1's
+3 = 9 +1's
+4 = 27 +1's
+5 = 81 +1's
+6 = 243 +1's
+7 = 729 +1's
+8 = 2187 +1's
+9 = 6561 +1's

+2 = 3 +1's
+3 = 9 +1's
+4 = 27 +1's
+5 = 81 +1's
+6 = 243 +1's
+7 = 729 +1's
+8 = 2187 +1's
+9 = 6561 +1's