first time growing avocado indoors.why does it look like there are almost no veins in the leaves. I don’t have any idea where to start because everything else about the plant looks ok.
The veins are all there. The picture you posted shows them clearly. It also show that they plant is needing some fertiliser. The entire leaf should be dark green not just the centre vein (see leaf in background for clear view of what I mean) The veins are dark green, but the rest is not. You want fertiliser made for either Palm Trees or Citrus Plants. These have extra micro-nutrient like magnesium-sulphate (Epsom Salts) that allows the roots to take up other vital nutrients like iron. These are two important micro-nutrients. These and others are found in these speciality fertilisers. You will find these micro-nutrients in other fertilisers as well, but not normally in high enough volume for avocados.
Here are some links to some examples of what you are looking for;