Meal prep is a great way to help keep you on track or get you going in the right direction. When healthier options are all prepped out and ready to go it makes it less likely that you'll grab a not so good option on the run.
So first and foremost the important thing about meal prep is to NOT over think it! Find a nutrition plan that works for you and stick to it! I have been following the same nutrition plan for a while now and it works well for me. I try to stick to an 80/20 lifestyle. I try to eat clean 80% of the time and have my not so good stuff 20% of the time. I also try to stay away from processed foods as much as possible. Don't get me wrong, I LOVE pizza, chinese food, and even fast food on very rare occasions but that's where balance comes in. Plus there's also those nights where throwing a Digiorno in the oven is just all I'm good for. The nutrition plan I follow is from the 21 Day Fix. This nutrition plan is so so so SIMPLE! (Plus the program comes with cute little color coded containers!) Everything is laid out for you on how many portions of each food group based on your goals. At this time I'm working on maintaining and growing muscle. So it changes for your goal and your target calorie bracket.

(Here's the portion containers that come with the fix! Super simple and easy to follow.)
So most of the time for my lunches I have a serving of some kind of fruit, 2 servings of veggies, and one serving of protein. Plus snacks.... Girls gotta eat. I try to keep my lunches under $4-5. That part is almost like a game. How many meals can I make for the lowest price?
The next thing I would recommend is getting yourself a nice set of meal prep containers. There are TONS of them out on the internet with so many different sizes, colors, bags, ice packs, color coded lids, blah blah blah..... Again, simple is best. Don't overthink it... If you love your Rubbermaid containers and they just work for you then stick to that! The one I bought came with seven containers. They have 3 different sized compartments and they came with an ice pack. I got them on Amazon for $10.38 as a Prime member. I would recommend dishwasher and microwave safe just for simplicity.

I usually prep 4-5 days worth of lunches depending on what I'm making and my work schedule. It saves so so so much time in the mornings and gets me out the door so much faster. I am NOT a morning person you can ask my husband. So anything to make the morning easier and so that I have to think less the better. I prep all at once and it takes about an hour or so.. It's so worth the time!
Hopefully this helped simplify things for you and will be a helpful tool to get you started.
Happy prepping!