1) To make a true Gimlet you will need to use Rose's sweetened lime juice. (Yes, I realize to some it might seem the same as lime juice and simple syrup - it's not.) I prefer a five to one ratio of Gin to Rose's - but you can adjust depending on how sweet you like your Gimlet.
2) A true gin martini is made with dry vermouth. 7:1 is the preferred ratio. Those of you not using vermouth are not drinking a martini. Not using as much vermouth became popular when "vodka martinis" became the rage - as the vermouth overpowers a nice clean vodka. In a properly made gin martini, the vermouth will smooth the gin but not overpower it.
3) You should REALLY try making a Vesper (although it will require additional purchases on your part) - it is my favorite drink with gin. It is the original drink ordered by James Bond in Casino Royale.
3 parts gin, 1 part vodka, .5 part Lillet, with a large twist of lemon. The hard part in ordering this at a bar is so few now carry Lillet (French appertif wine - available at Spec's) - but if you are in a respectable bar that knows how to make cocktails you should have no problem.
Not knowing what type of Gin you have limits my other suggestions... If your gin is cheap?
http://www.youtube.com/watch?v=0Cxr1-b6Xkc[This message has been edited by mwesson (edited 6/20/2012 8:46a).]