Please don't feel like you've failed. It's not the number of cigarettes you've smoked, it's how many you've avoided by vaping - and that number is cumulative. So cheer up!
Slim e-cigs for the purse: there's a few 'tank' systems I like, the Innokin Lily (it's got bling) and the Joyetech Ego C-Cab,(removable battery). Very e-ciggy, no frills. Both can be converted to 510 and so other atomizer/liquid delivery systems are an option. Innokin also has the iClk 1280 which is an advanced beginner vv/vw penstyle/clearomizer combo you might like.
eliquid: Flavorings have a very long shelf life - but in solution they fall off over time. Doesn't mean that the eliquid is bad but that previously yummy flavor may not be so yummy now. Nicotine itself has a shelf life dependent on concentration.The higher the concentration of nicotine, the lower the shelf life. 6mg/ml keeps longer than 24mg/ml for instance and 6mg eliquid will stay a lighter color longer. Oxidizing nicotine darkens liquids and over time will impart a wet-dog, gym-shoe, over-peppery taste. (some people taste nicotine as a slight peppery tingle, that's normal, but really over-oxidized nicotine is really really really peppery/wet-dog and foul tasting). I've never found a way to successfully disguise wet dog.
Vape some test puffs first (see wet-dog above) before filling your device up. If your liquid tastes close to flavor, and vapes like it's supposed to, then you're good to go, at least while you place an order for some fresh liquid. If the eliquid looks clumpy or has thingies floating in it, don't vape it. If it has 'separated' into an upper and lower layer, shake it well and see if it reincorporates and if it doesn't, don't vape it.
and, welcome back to vaping!