How many quarts of each nutrient will i need to buy for 3 plants?

I have 3 plants 2 weeks old and am wondering how many quartz of each nutrients should i buy?

None...Quart prices are a ripoff compared to gallon. Buy gallon size.

I can make a litre last a month and a half, but I am hydro with very light nutrient feeding. I think its based on the brand you are looking at what you should add. Just never add as much as the company says they just want you to max your plant out on nutes so you can buy more. Very risky. But yeah, it is cheaper in the long run to buy gallon.

Don't buy liquids, buy solids. Pounds.

I grow 3-4 plants at a time in a neutral (no nutes) soil.

one quart is plenty for more than one grow. I use dynago. I have 3 plants going 2 weeks into flower. I water about twice a week, 2 gal each time total. Nutes every other water. Each gallon, so two per week, gets no more than about 1-1.5T of any nute.

Look up your brand's schedule, assume you will use about 75% of what they recommend and you can do the math...

What nutes are you going to run? 50% of recommended is probably better math.

Im thinking about Dyna-Grow or FoxFarm nutes...

Dyna fp is pretty good. get a small bottle if you go that route it tends to fall out of solution after a while.