I agree with what everyone here has said. I’m going to share with you some thing that I wish I had known when I first started out. I trained for several years without getting results, because my diet, supplements, and work-outs weren’t done correctly. I finally decided that if I wanted results, I needed a trainer. I learned quite a bit. I don’t use a trainer anymore, but I still see results all the time. I will discuss some things that were flawed in your proposed work-out scheme and give you some pointers on how to develop a plan that works.
You are 6’1" and 160lbs. You are SKINNY. You do not need to fast. I will discuss diet later. I know you don’t want to train legs, but you have to realize that everything is connected an you do NOT want to develop imbalances, which can lead to injury.
Also, squatting and deadlifting are the two main moves for legs. They are, when done correctly, in and of themselves truly full body exercises. If you want a bigger upper body, squat and deadlift. I have gotten more gains on my back from deadlifting than from anything else. My core strength has gone through the roof from squatting and deadlifting. You are shortchanging yourself and cheating yourself if you are going to skip those in the name of only training your upper body.
Don’t over-think this and don’t spend a ton. Just take what you need to get you through a work-out. Know what is in your supplements and why you are taking them before you take them. Read articles about them. Choose the best ones for you. Take a pre-workout. Many have stimulants in them. If you are working out before bed, you might not want one with a stimulant.
I love the ones with stimulants, but I work-out in the morning. If you want to get big, take creatine. I take mine post-workout because my pre-workout has creatine in it already. Take whey protein to supplement your diet. Know what is in your whey, because not all wheys are created equal. I don’t know how much I like the so-called mass-building wheys. I think they are just a bunch of sugar for the most part. I have taken one before, but I prefer a whey with low carb (I like to cut a lot, although I do cycle between bulking and cutting). Know how much carb you want in your whey, and get the right whey for you. The whey I take has about 4g carb per serving.
You are under-weight. You have the opposite problem of so many people. You do not need to fast. My advice is to eat small meals every 2-3 hours that consist of clean food. So many people like to over-think this. For someone like you, I would not make this any harder than it needs to be. Eat a meal that has a good amount of protein (chicken, eggs, Greek Yogurt, lean beef, fish), clean carbs (fruits and vegetables, sweet potatoes, rice, oatmeal), and clean fats (extra virgin olive oil, omega-3’s). Eat until you don’t feel hungry (but not until you are stuffed/full). Some people have to get really picky and count calories, fat grams, carbs, protein. I would read articles on diet and know what those ranges are for your target weight, just so you know what you are looking for. But, in your case, you do not need to cut and you probably are not prepping for a bodybuilding contest, so just keep it simple, eat foods you like, eat often, know what is in the food you are eating, and keep it clean.
There is a lot to say here, but I will try to keep it as simple and straight-forward as possible. If you are new to lifting, you probably should be doing a full body work-out 3 times a week. The work-out should last probably 30-45 minutes. That is your best bet. Choose compound moves (moves that involve multiple joints: e.g. bench press, squat, deadlift, bent over rows) and do 3-4 sets of 8-10 of each. Have about 90s rest in between sets. Each workout should involve an exercise for chest, back, legs (quads and hammies), shoulders, and abs/core. Know how to do each exercise before you do them. There are videos on youtube and various websites. Watch them. Know your form. If you are doing barbell bench press, have a spotter or use the Smith machine. If you don’t know how to do an exercise, don’t do it. Don’t trust that some other dude in the gym is doing an exercise correctly and copy him. Plan your work-out, watch videos and read articles. There are so many good articles on proper form for bench press, squat, and deadlift. Read them. Watch the videos. On your days off from full-body workouts, if you feel the need to work-out, you can do cardio. If you are trying to bulk, keep the intensity low. When it comes to cutting, high intensity interval training will be your friend. There will come a point where full body workouts won’t cut it for you anymore. You will need to re-visit your split and probably change to more of a 4-day split such as a push/pull split or an upper body/lower body split. You will want to start those work-outs with compound moves and finish it with isolations. Keep the work-out simple, about 6 exercises per workout. Give that time, and it may not be enough for you, and you might then want to change to more of a bodybuilder split where you train one muscle group per day (i.e. Monday-Chest, Tuesday-Legs, Wed-Arms, Thurs-Back, Fri-Shoulders). Once every 6-8 weeks you probably want to deload. I usually change my work-outs up at least once every 6-8 weeks. Sometimes during that period I will treak the rep ranges, rest, or intensity. When you write your work-outs, you should know what your goals are beforehand and plan accordingly. The exercises you choose, the weight you choose, and the rep ranges will all be defined by your goals. Read articles about rep ranges (gaining strength is 1-6 reps, gaining size is about 8-12, gaining endurance is 15+ reps per set) and total amount of reps you should do. But, most important, make sure that you are training every part of your body if you are going to train. If you start skipping major muscle groups, you will develop imbalances, it will affect your physique, and you may develop injuries.
I’ve been training for years and I am constantly reading and watching videos. I am constantly improving my form and learning new things. But, if you want success, that is what you do–keep learning.
I hope this helps.