I actually really wanted to become a dietican/nutitionist/personal trainer sort of thing, till my father crushed my dreams. Most things you stated, are quite incorrect.
1) Depending on your body type and life style, mass builders might be the solution for weight gain. Like for me, I could never gain weight ever. The only way was 4-6 proper not really balanced but meals with lots of low gi carbohydrates (with atleast 30g protein), and between my high protein/carb meals I would have to have a mass shake for the extra boost in carbohydrates, which were techniquely complex carbs (Maltodextrin), which totaled to about 700+ grams of carbs per day. Carbs give you size, protein re builds muscle fibres. But carbs also promotes protein-synthesis. So having them together = max gains. If you just have protein lol, nothing will happen. It will just become waste in your urine (well what ever isnt being used). And also never rely on supplements, combine both together, because supplements absorb incredibly quick compared to lets say eating a can of tuna.
2)Mostly true point, but never repeat same workouts constantly change it up, do pyramids, slows/fasts, change things up every time, you need to shock your body, and make it think "oh fuck were scrawny and shit we n33d mor muscle" constant repetition means slow growth or none at all.
3)Dead lifts are great, but so are squats (Acctually increases the testorone hormones <-- More growth)
Big tip - Cause your on creatine, drink shit loads of water. And get plenty of sleep. and if your an Ectomorph, eat right before bed (carbs/protein).
And also dont worry about getting some extra fat in the process, easily lost later on, its not even funny how easy it is.
Saying that I did experiment, for 3 years with this all. I started at 65kg ish, got to 84 kg.
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Pic 1 - about 81 kg.
pic 2 - 84 kg
pic 3- back from schoolies was about 75kg lol. (alchol 7 days straight didnt really eat anything bar like lettuce as i couldnt keep any food down haha. but i did cut down to 78kg from 84 was about 6% body fat at the time. maybe a little bit more