This is a common concern a lot of newer players have, and the short answer is use your best judgement. A general rule of thumb I think is good to follow is that unless you KNOW you will benefit significantly from the extra gran, don't recycle. An example would be a powerful EX is released and you're 100 gran short of nabbing a 3rd pack for a playset. You know what you're getting for sure, so I think the recycle can be justified.
Just remember, you could be here for a while and someday you may want to try a new type of file. Don't recycle for gamble gran because you think you'll never use a card. This is an online game, and as such erratas can occur and one day that "useless" card you recycled is not so useless anymore.