I've got to sleep soon (early start) so...
IF your Blu is a standard eGo fitting, you can buy most tanks called CE3, CE4, CE5.
CE4s are the standard one. Good ones will last for 10 refills, bad ones maybe not. (I killed a "stardust" one in under two days once....)
Innokin iClear16 , Kanger EVOD, Kanger T3S, Kanger mini Protank all use eGo thread BUT they have a replaceable atomizer section.
so, the cost is either go disposable at £1.60 a go OR buy a tank for £3.50 and change the coil for £1.20. Not much difference in the price (even I don't try to save 40p!!) but the rebuildable ones are generally better performance-wise.
If you like the look of the Amazon ones, bag a pack, why not.

See how you get on.
Beware of buying posher tanks on ebay/amazon as lots are fakes. If you decide to get a tank you can replace the atomizer on, have a look at MYEPACK or VAPE ESCAPE. Whatever, make sure you buy an EGO one. 510 or 808 won't fit.
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If it was me spending your money, I'd buy re-useable, of course. They vape better and you can take them apart for cleaning, rinse out horrible flavours, all that sort of thing.
Have a look here, when the time comes for more liquid....
LiQuid - Incredibly Awesome UK Made 10ml E-Liquid For £1