Row to draco as in game, 2 draco=3 draco (but this goes cheaper depending on the amount of draco you are buying)
GC to draco =1.5k gc for 1 draco
In terms of 5/10/15, depends on the buyer and seller, since with $ you can have your own price, but ideally:
5 VD= 60-70 draco
10 VD= 120 Draco (Since t1 draco is 10$)
15 VD= 150-180 draco
20 VD= 240 draco (this is what seller and buyers are agreeing in the BTA)
25 VD =240 draco +add (many bta i see, people offer 240draco or t2 uber+around 100 rows)