Hey man, you can give VT here a shot they got some pretty rad juices. I would recommend trying Dulcis or Mentha
Also tastyvapor has a great deal on liquid. You can buy 1 30ml bottle of 48mg nic for $15.00 and a 60ml doubler ( liquid without nic ) for $10.00 and mix them all to get 90ml of16mg E-liquid all for $25.00
just keep in mind it will take a little bit longer for you to recieve your order from them as they mix there own E-liquid to order.
For you second question of VG vs PG
PG = more throat hit
VG = more vapor
I found that mixing them togethor is the best way to vape. evan a 90/10 of PG/VG is very noticable.
PG is Propylene Glycol. The difference between the two is vapor production and flavor. VG is supposed to give more vapor but it can cut the flavor a little, while PG does the opposite. This is kind of subjective and I've heard both sides of the story. People get a PG/VG mix to get the best of both worlds. I don't particularly like VG or mixes. Each person is different so what may work for some, doesn't work for you. A lot of this game is trial and error.
By the way, 25 carts for 25$ isn't a very good deal. I would stick to direct dripping or refilling the carts. You can get Juice on tons of online vendors, I would check out the Certified Suppliers of the forum. I've ordered Juice from about 20 different places, some I liked, others not so much.