For the newer folk - you got a shiny new gold vehicle ticket - what to buy, what to buy…decisions, decisions… 
The main DO for BP vehicles is to buy something that gives you a major advance along teh campaign levels - something you would otherwise only get after a lot of grinding.
For example a long while ago I got the T-50 in Moscow while I was still using BT-7’s - it meant I had a Lvl 29 (?) vehicle at about level 10… with the added advantage that the T-50 was pretty OP and ruled the roost in those days! Happy times! 
And that T-50 squad is still in my main line-up (albeit with Tanker III crew) alongside a T-34.
DO - check that your crew can use the vehicle or plane!!
Eg as a noob I got the Me-410 in Berlin, thinking to use it with my Stuka crew - but the Stuka crew can’t fly the Me-410!! 
The BP Me-410 is a great plane - but that’s no use if you can’t fly it!! I eventually got to the Me-410 through grinding. Certainly the BP 410 is better than the stock version, but I then got the BP Fw-190 D-12, which is better again - so the 410 only got maybe a dozen games and sat around for a year or more wating to get those!! 
Total waste of a gold order!!
DO NOT buy something that you already have from the grind or that is only a level or 2 away!! Converse of the first item - you are not getting enough of an advantage to justify using the gold order. BP vehicles and planes are noticeably better than their stock versions, but bronze orders and upgrade tokens are much more common than BP Gold tickets - so use them to upgrade the stock version - even if it comes out a little worse than the BP version at the end.
