When I first start a game I play my coins real tight. The only things purchased are land upgrades, plowing, and seeds. The exception being some items purchased to help make the next level when I am real close.
I get frustrated with myself when the math doesn't work and I run out of coins before planting all my fields so I made this calculator to remedy the problem. Choose your crop, how many fields you want to plant, how many coins you have, and it will give you the cost of plowing, seeds, and coins left or needed for those fields.