It is difficult (by design) to get Blueprints via the Tournaments. But that is the only free way, so far. You must be a member of a Fellowship to participate in tournaments. The more active folks you have in a fellowship that wish to participate in a tournament, the easier it is to get a blue print. Like many other points in game, it is key to set a prioritized goal. Our fellowship has roughly 15 players that actively participate in tournaments. We choose to only try to win the 10th chest during the Planks tournament (one of the easier ones). We do not "Go for it" every planks tournament, because there are many other things going on that tap resources. About every other planks tournament is a target for us. That means we "Go for it" about every 18 weeks; plenty of time between attempts to build up goods and troops for the effort. So far, every time we have targeted the 10th chest (to win a blueprint) we have achieved our goal.
Difficult, but not impossible with preparation planning, an coordination.