Well I would say don't waste your money on fanta because the future of how they are going to implement things remains uncertain. They just screwed over/angered a large portion of the community last event by having Stiria be a bt reward with only 2 days left of competing, meaning only one person on the server got her.
However if you're determined to spend it's better to come up with a plan of how you are going to get something that you want. The dream packs seem pretty interesting if you want to spend over a long period of time and eventually get a 7*.
If you want to spend over a short period of time PC the cards that you like before you buy TE and decide if it's worth it to buy them.
Or compete in different events without spending and see if you like competing in them, and set a goal for an event you'd like to compete in by using money.