I am fairly new at hatching, and by no means an expert, but I would think that you shouldn't try to hatch the first bunch of eggs after adding the rooster, especially if your hens are relatively new layers. I got started by borrowing a friend's incubator and some eggs to "get the feel of hatching." This may or may not be an option for you. I will warn you that hatching is addicting, and nerve-wrecking. The best solution is a broody hen, but it is a lot of fun to hatch your own.
I've considered many incubators at all price levels. There has been a great amount of information on BYC about them and of course, everyone has their own opinion. I will mention a few that stand out to me. These are my opinions, so you will need to do your own research.
From what I can gather, many people start out with the styrofoam incubators. The GQF Genesis 1588 with the 1611 turner has been listed as one of the more reliable models. It has an electronic thermostat with a digital readout, large picture window, and forced air fan. A very good starter incubator with a 42 egg capacity (with turner.)
Brinsea makes wonderful incubators, but they are a bit more pricey. Their incubators are plastic and hold different number of eggs at different price points.
Brinsea has the best prices for their own incubators, and you can easily find a 10% off coupon code. In addition to sales, they also, on occasion, offer scratch and dent models at deeper discounts. If you purchase a
Brinsea product, remember to register it immediately to get an extra 2 year warranty on it.
The Reptipro 6000 is a new model that looks similar to a small refrigerator. It holds 32 chicken eggs (with turners) and is available through incubators.org at a very reasonable price. There is an entire thread on BYC devoted to the Reptipro.
Larger cabinet incubators are more expensive. The GQF Sportsman 1502 is an incubator and hatcher in one. Because the humidity is boosted in the last 3 days of incubation, many people will put their eggs in an additional incubator at lockdown so that they can stagger their hatches and reload the first incubator. Otherwise, they have to remove the egg turner and bring up the humidity in the incubator.
I have some specific documents about hatching, and would be happy to answer any questions that you might have, if I can. There are many people on BYC that have been doing this a lot longer that can help as well.
Blessings!!!