Life Like starter sets can be had for $75 or less. Many are headed by their GP-20s, GP-18's, or SW switchers. These are good engines as they are detailed and run nearly as well as Atlas but aren't easy to upgrade to DCC. The rolling stock is so so and so is the power pack. The sets come with Powelock roadbed track which is good for circle running but should you expand it is not real good stuff because the switches are sucky and you are limited to 9 3/4" radius.
Most Bachman sets suck. Their 0-6-0 pennsy style switchers with tender are decent sets. Their sets with 4-8-4 Northerns are iffy. They come with EZ track which is like Power Lock track. They also make Spectrum steam sets which are good but overpriced.
Kato starter sets are an excellent choice and will set you back around $100. They don't come with a power pack so add another $30 or $50 for a power pack. Kato power packs are good packs.
Atlas code 55 track is excellent track. Micro Trains and older Atlas with large wheel flanges wont work with it. You will need to change out the wheelsets. Most Micro Trains cars include the proper wheelsets as extras with their cars. Most recent cars come with the proper wheelsets installed.
Peco code 55 works with everything as the inner ties are set lower to accomodate larger wheel flanges. It does not look as good as Atlas code 55 and is more expensive. Especially switches.
There is great selection of quality engines by Atlas, Kato, Intermountain, Microtrains, Con Cor, and Life Like. Bachman Spectrum steam and Life Like Heritage steam is good stuff too. Bachman deisels suck. Model Power steam is OK.
Hobby Lobby carries some of the better Life Like and Bachman 0-6-0 sets I mention
This link is to a 40% off cupon and you can get a Bman 0-6-0 set for around $35 which is a good deal.