I agree with the general consensus that duranium, gallicite, and corundium are the minerals I have the most trouble with at various points in a campaign.
I do suspect, however, that a lot of players (myself included) tend to under-specialize their economies with respect to these minerals, because intuitively it's difficult to accept that mining an asteroid with 100,000 tons of 1.0 gallicite, for instance, is better for your economy than mining an asteroid with 100,000 tons each of 0.8 accessibility gallicite, uridium, tritanium, and boronide. The latter asteroid is more resources per mine, but if you're running a deficit of gallicite and a surplus of the other three that indicates that you don't need the other three, but you definitely need the gallicite. Unintuitively, when it comes to mining often less is more.
I for example tend to experience a crunch relatively early in a game because I am reluctant to move infrastructure away from Earth while it's still producing 5.0 or 6.0 of total mineral accessibility, even though duranium might be down to 0.6 and gallicite down to 0.5 while my stocks of the "other TNEs" are sky-high and don't need the help.
That said, for gallicite particularly I think there are more creative ways to solve the problem. If the main consumption of gallicite comes from engines, one approach is to not build engines - often it will be fine to refit a ship with older engine tech with new weapons, armor, etc. and it will still have sufficient speed to do its job (particularly if one plays mainly against NPRs which tend to have atrociously slow builds). One can also use lower-cost engines or even commercial engines for many warships, for example large missile battleships or carriers do not need to have high speed in a battle, while PD escorts or fighters may need more speed but are small enough not to be too expensive to put fast engines on. I think it is good that the game economy incentivized creative fleet design and forces players to make decision between an optimized fleet or an affordable fleet, this keeps things interesting as the game goes on.