Poor mans Iso 8
I've been reading a lot about the woes of lack of silver so I thought this might help. Credit for this goes to one of my alliance mates but Ive been using a version of this method for a while.
The cheapest way to boost cards.
For the first 15 to 20 levels use common feeders to boost the target card. (Thank you comments section)
Since the first boost to a card is the cheapest, you can take advantage of this by boosting a fused rare card (rare plus) with ten common feeders. This should get your rare plus card up to level 7 to 12 based on whether you luck into a ultimate boost or not. This boosted rare plus card is a poor mans iso 8. This single card when used to boost any other should give you approximately 250 Xp. For best results make 10 poor mans iso 8 cards and use all 10 to boost the target card. This gives you roughly 25 levels, more than 35 if you hit an ultimate boost. The cost savings when you use this at higher levels is extremely large.
The only down side to this is that it is a less efficient way of boosting. You end up using more feeders overall to get the same number of levels, but its way cheaper than any other method.
There are a few excellent posts about boosting done by quite a few people, can't remember exactly by who off the top of my head, but look them up for more in depth mechanics and analysis.
(Zbergs blog post is the post I'm referring to, there is a link in the comments section which i would highly recommend if you want more information about card boosting)
First post, so go easy on me if I've made a mistake or you have a different opinion. Cheers!