My First Hydroponics and Growing Experience

Hello Everyone
I'm new here and new to gardening.
I recently just build myself a flow type of hydroponics.
Now I want to grow some lettuce, tomatoes, fruits etc. but I don't know anything about gardening or using the hydroponics for growing.
I was wondering what type of nutrients/fertilization I need to buy?
Basically I don't know what type of food to buy for the plants. I am going to start to grow lettuce and tomatoes first. Will this be okay? Do I need anything else?

General Hydroponics Flora Series QT - FloraGro, FloraBloom, and FloraMicro

General HydroponicsGH3254 General Hydroponics Rapid Rooter Tray, Single Pack

P.S. Can anyone recommend me a ph meter to buy on amazone. Like which one you recommend thanks?

This is kind of hard to respond to. There are countless books on hydro and you could get one of those. They probably don't recommend any particular fert, but instead discuss nutes and rates and time and temperatures... you can see that this isn't easy to respond to in a single post. So, what to do? Much of hydro is experimental and you'll learn from mistakes. You'll have to determine what parts per million of fert, or Total Dissolved Solids, to use for the different stages of growth. The smaller plants require less and need more as they grow. Personally, I've discovered it's best stay as simple as possible. You can use a 3 part fert if you want. There are 2 part ferts or even 1 part ferts, where pretty much everything you need is contained in one bottle. It just doesn't have a long shelf life. For pH meter's, it's more of what you can afford. Spending alot will buy you better accuracy, but may not really be necessary. I would suggest you get a book on hydro for veggies.