When planting tree seeds try to put them in the pot you want them in for a few months, so a 1 gallon nursery pot or bigger. Or, go right into the ground. It's better nto to transplant young seedlings until they're well established and a bit woody - the winter after you start the seeds.
I've starting anything from maple trees to pine trees but placing the seeds in posts full of half compost and half sand and making sure they got 6 hours of morning sun and then shade the rest of the day. My plants are in pots on the East tisde of my house. Bright warm morning sun and then around 1 the shade starts to shift over them as the sun passes over my house and they don't burn up in the hottest part of the day.
How big are your pots? If you need to, move them to something bigger, even though I said it's better not too. It's better to start them in something big so you don't have to move them, but move them if they need the space - they will just stop growing and eventually die if the pot is too small - go ahead and move them. Water every day, don't miss a day, and water well. Remember, in a pot all of that water drains out and the plant is left to wait until the next time you water! Compost helps with that because it absorbs and retains more moisture. If you are going to move them - half sand or soil from your own place, half compost. Skip the shortlived potting soil.
Whenever possible, avoid synthetic fertalizers (like miracle grow). It's bad for your soil and not great for the plants. Adding compost to your pot when you plant is best. Afterwards, compost tea or worm tea *basically, the compost or worm excreiment soaked in warm water out in the sun like you would regular tea, then the "dirty" water used to water your pots* works really well.
You can actually distrub roots quite a bit and have a very succeful transplant rate. But that takes some practice. So, try not to distrub the roots and just move the whole clump in your pot if you transplant them into a bigger pot or the ground. Let it dry out just enough to make a clump you can handle. Freshly watered potting soil will crumble apart when you try to take it out of the pot.