The biggest mistakes beginner make starting seeds indoors are:
1) starting them too early
2) not enough light
They are related because the distance from the lights is a huge factor in intensity. If you double the distance (say from 2 to 4 inches), you cut the intensity to 1/4 of what is was, so the seedling start ok, but as you raise the lights, they get less, so they "reach" more for the light. It's a natural response to try to reach sunlight over the competing plants.
The biggest favor you will do yourself is to wait. We want to rush to get a start on spring, but IMO, the only seeds that should be started now are peppers and broccoli/cabbage/cauliflower. Even those is pushing it a bit, a week or 2 from now would be better. Definitely hold off on tomatoes, they are warm weather plants and putting them out in April is cruel to them. Unless you know you have the light intensity to handle larger plants, wait a month before starting the tomatoes. Don't believe me? Do it both ways this spring and see which ones are doing better in July.
If you've already got tomatoes going and they do end up too tall and scraggly, you can transplant them deeper (don't do this with any other plants, only tomatoes). You can even strip off the lower leaves and plant them on their side, buried up to their lowest remaining leaf. This works in pots or the garden. Tomatoes are the world's easiest plant to grow from cuttings, they will sprout roots anywhere on their stems (few other plants can do this - those in the mint family also come to mind). You can easily root tomato cuttings in a glass of water on your window sill!
People like to see big tomato plants when the put them in the garden. That's all marketing to sell you more. The ideal size is 3 - 4 inches, but smaller is better than bigger, IMO. Early May is when you want to plant them out, not April.