Definitely get a wide range of types of flavors if you're looking for something that you can stick with all day. I love fruit flavors, but I get sick of them if it's all I have when I'm at work. I'd recommend at least one fruit flavor, one minty flavor, one sweet/dessert flavor, one tobacco flavor, and one semisweet (? I can't think of a word for it) flavor like coffee or cocoa. Also, since you're a menthol smoker, make sure you pay attention to the descriptions of the menthol juices you order. Some will be menthol tobacco, some will be minty tasting menthol, and some will just be straight menthol, like a cough drop (which actually comes in handy to add a touch of menthol kick to other flavors). Anyway, my point is that you can't know what you will like until you try it. After the pre-filled cartridges that came with my PV, I decided that I didn't like tobacco flavor and I didn't order any in my first couple of orders. After reading a lot of praise for BackwoodsBrew's tobacco flavors, I tried one out and now I stick with tobacco for all 8 hours I'm at work during the day. Before I started, I thought that I would love cocoa and coffee flavors, but those are actually the ones I use the least. What I seem to have settled on is using tobacco flavors during the day and then at night switching to a drip tip and switching it up between sweet and fruity flavors while I'm relaxing.
And here's a list of some vendors I bookmarked that were recommended to me in a thread I started about e-liquid:
Ms. T's Bakery - Known for sweet/dessert flavors
FreedomSmokeUSA
Backwoods Brew - Known for tobacco flavors, but his other flavors are great, too - He's on vacation right now (it's a one-man operation), so you'll have to wait if you want to try his juice out
Alien Visions - They have 100% VG and 10/90 PG/VG juices if you like LOTS of vapor or have problems with PG - Also closed temporarily
Vermillion River
KickBassVapor
want2vape
Tasty Vapor
Vaperite
VaporBomb
Gourmet Vapor