The default concentration for a typical putative 30 ml bottle is 2.5 mcg/spray. I have been told from many people that 2.5 mcg/spray is too weak and definately not the way to go, because you’ll end up having to spray too much if you want any noticeable/desirable effects. My question is this: what is a good mcg/spray to buy without it becoming too expensive? Keep in mind that this question is for anyone interested in buying putatives and wants to try out MANY DIFFERENT ones over a length of time. Thanks a lot. 
given the to-go are at 12.5, I would say look into a 30ml around that strength..
thanks mike…any other suggestions? 
If you are just testing the putative get the 12.5 to gos. If you are getting them for “roll your own” mixes just make sure you get them all in the same strength. It make sfor easier calculations. I buy them all at either 20mcg or 40 mcg because I mix in to gos and 1 spray of 40mcg or 2 sprays of 20mcg dilutes in a togo of perfumers alcohol to 1mcg per spray. Others use 30mcg and mix in 30ml bottles for similar reasons. Check Mark-In-Dallas’s journal for details on that method.