IMHO, lots of money is wasted on starting plants WAY too early.
What's most important, is soil temperature!!!
Tomatoes, for example, aren't going to do anything serious until the soil temperature hits 60 at root depth, and they'll do even better when the temperature hits 65 degrees—above that, they'll take off like a rocket.
Having the seeds germinated and ready to go, as tiny seedlings, when the soil temperature hits 60 degrees is enough.
One year, I sat out some very tiny Matt's Wild Cherry seedlings on the 26th of June—that's considered very late around here, especially for such tiny seedlings.
This was back when I was stacking cages made from concrete reinforcing wire as supports for tomatoes and other stuff.
The plants reached 15 to 18 feet before they were killed by frost!
Leggy (or spindly) plants can be caused by not only insufficient light, but also too much heat as well as fertilizer issues.
Having said that, having leggy tomato plants isn't the end of the world—just pinch off the lower leaves and trench plant them—they'll develop roots along the trenched stem.
But, you've created much more work for yourself than is necessary if you've reached the point of having to worry about leggy plants.
