What is a good way for a beginner to start sous vide cooking?

Start by estimating the accuracy of your temperature sensor and controller. You're going to need to do some comparisons with reliable thermometers for this step. I'm guessing you don't have any laboratory grade thermometers at home that have recently been professionally calibrated. (Who does, really?)

Start by finding two or three digital cooking thermometers (preferably different models) that seem trustworthy. Then calibrate your PID controller by measuring the temperature of a mixture of equal parts crushed ice and water. It should be 0 °C. While you're at it, use the ice slush to check the accuracy of the cooking thermometers you found. Recalibrate or replace them as needed. Finally, heat some water to around 60 °C (or whatever temperature your think you'll be using most often for cooking). Then measure the temperature with your PID controller and the cooking thermometers. That should give you a pretty good idea of how accurate your PID controller will be during cooking. (If you find that your PID controller is accurate at ice temperatures, but quite a bit off at higher temperatures, you likely need a new temperature sensor.)

Sous vide accuracy is frequently in the neighborhood of +/- 0.1 °C, but +/- 0.5 °C is often good enough. I'm not sure what "low accuracy" means, but let's say, for example, that you estimate your accuracy to be +/- 2.0 °C. In that case, simply raise the temperature setting by 2 °C to compensate for the margin of error. It might result in a different level of doneness than you want, but the food will probably be safe.

Take a look at Douglas Baldwin's A Practical Guide to Sous Vide Cooking. Not only does it have some excellent recipes for beginners, but it also has some great safety information. If the food is to be consumed by pregnant women, you don't just want it to be cooked. You want it pasteurized. The guide includes tables for looking up the pasteurization time for fish, poultry, and meat (beef, pork, and lamb). If the meat is starting frozen, add about 30 minutes to the cooking time. If a recipe's going to take too long, use the tables to adjust the meat thickness or temperature in order to reduce the cooking time to your preference. Keep in mind that your shouldn't start the timer until the food is in the water bath and the water is up to temperature. So, save time by heating the water first thing when you're ready to cook.

I would direct yourself to this handy table from Dave Arnold who is somewhat of a figurehead in sous vide cooking

http://www.cookingissues.com/uploads/Low_Temp_Charts.pdf

It will show you the differences in textures and doneness for different proteins and even eggs and give you an idea of what you would need to do. I have built two DIY immersion circulators thus far and have had good success using a well insulated cooler and zip top bags. I would also suggest you direct yourself to http://www.chefsteps.com/ to learn more about technique.

No question in my mind -- if you want it done in under two hours and don't need precision, I'd go with some form of undersea critter. Shrimp come to mind, and a demonstration video can be found on youtube.

Eggs. Easy-peasy way to get started and very hard to under-cook. Just try for a simple custard or soft-boiled egg to start. You can mix-and-match fats/oils and spices in different bags along with different cooking times and temps to see what happens.

http://www.seriouseats.com/2013/10/sous-vide-101-all-about-eggs.html