Which seeds should I start with ?

Grow lights and a heating mat are very helpful for starting seeds. I grow for a roadside stand and could not start my seeds with out the heat mat for sure. We don't usually have enough sunshine to go without a grow light either. Most of the seedlings need the extended day length that the light fixture provides.

You can improvise for a heat mat, usually, using a heating pad set on low, covered with plastic so it doesn't get wet and short out.Use a thermometer to check the temperature, it shouldn't be over 85f.degrees. A light fixture can be as simple as a florescent shop fixture suspended to hang directly over the seed trays/plants at nearly the height of the seeds or plants. the farther away from the plants the more the plants will stretch for the light making spindly leggy plants.

(We have a Menards close to us and now is about the time they sell heat mats for about $20.00, which I buy them and haven't had any problems with any of them)

On to the seeds, some varieties are harder to start than others. tomatoes being the easiest and peppers next to hardest and eggplant the hardest for me. Tomatoes rarely are hard to start, they hardly even need the bottom heat, but I still wouldn't try without it. Peppers and eggplant can take quite a while to germinate and grow so give yourself enough time to get them started and big enough to put out in the garden. I usually do about 6-8 weeks for tomatoes a 10 weeks for eggplant and peppers once they have germinated...give the peppers 1-2 weeks to germinate and eggplant can take 2 weeks, too. Cole crops don't need bottom heat, but it won't hurt to use it, mostly they need the light.

good luck!

EDITED: I also cover the seeds with a clear domed cover to keep the media moist. the heat pad can dry them out quicker.

This seed starting information is also applicable to flower seeds, IF flowers were what you were asking about. I inferred it was vegetables, but after re re reading it , it could be asking for either. sorry if I mis-read your thoughts.

Clay, do you have full sun or shade or both to work with?

Marigolds are really easy
zinnias are very susceptible to downy/powdery mildew making then on my "no" list.
impatiens really aren't that hard, the seeds are just very little.
Lobelia likes cooler weather to be productive, the seeds are like dust.
sunflowers are very easy, but you just need to plant them outside, not in the house.
rudbeckia is pretty easy, I grew them a few times, there are many sizes and colors available and the texture of the leaves is different.
Petunias are not hard, but thy start out very tiny as seedlings and take a few weeks to grow to a not so fragile size.
Nasturtiums, huge seed that needs nicked or soaked to germinate.
Coleus is a great shade plant and easy to get started.

Just remember that all of these need bottom heat to germinate well and light light light.