Weight Gain

In general you want to eat >0.6g/lb of protein, ~0.4g/lb of fats and the rest carbs. You can play with your carbs and fats a little to see what works best for you, but that's a good starting place. Eat enough calories to gain 0.5-1lb per week.

For a workout routine. Pick a structured routine that focuses on progressive overload and compound exercises.

Cardio is optional for the health benefits, but limit it to an hour or less per week so you can recover more effectively from your resistance training. You can break up the cardio into multiple sessions. I like to do no more than three 20 minutes sessions of HIIT per week.

Sups aren't necessary, but if you're going to take any, take 5g of creatine monhydrate per day. Preworkouts can help too, but just be careful since a lot of the supplement industry is underdosed and overpriced trash. So make sure you research the ingredients and probably just make your own from bulk. Examine.com is a good resource to see what ingredients are effective and backed with clinical studies.

Stickies are here if you haven't seen them yet:
https://community.myfitnesspal.com/en/discussion/10226536/bulking-for-beginners/p1
http://community.myfitnesspal.com/en/discussion/10049766/bulking-a-complete-guide-for-beginners/p1
Don't waste your money on supplements. They exist so that pro bodybuilders can earn a living. Even creatine will make such a small difference you probably won't even notice. Once you get closer to your genetic potential, your gains will slow down, and you may find it useful to spend money on some supplement that will maybe possibly give you a tiny performance bump.

Personally, I would follow a structured program for a few months prior to bulking to address the neurological efficiencies and then transition to a bulk. Essentially, your muscles will become more efficient prior to adding new mass. This doesn't mean you won't see some muscle development if you start now, but it won't be as optimal.

With that said, several good programs to start with are StrongLift, StartingStrength, Ice Cream Fitness, New Rules of Lift (for abs, for life) or the lean muscle diet (These latter two are books).

http://www.bodyrecomposition.com/muscle-gain/beginning-weight-training-part-1.html

Here is another good series (4 parts), that can be beneficial to your overall journey.