I've cleared the game on the normal difficulty, and now I'm going back over it again in 1999 Mode. One thing I noticed during my first playthrough is that there's just not enough money to buy everything - weapon upgrades and vigor upgrades are particularly expensive.
I spent my cash in my last playthrough willy nilly, but I feel like with the increased difficulty I need to make some more considered decisions. My money and salt budget are likely to be very tight.
Are there Vigor upgrades that are overpowered or essential for play at higher difficulties? Are there any in particular I should ignore outright as being completely useless?