Just gonna add on to these points:
1: While making the right decisions to KO the Pokémon on the field is of course important, you also need to make proper decisions in the macro. An easy example is to not KO Indeedee as Gardevoir sets up TR to make sure Torkoal isn't on the field in TR at the same time as Gardevoir. Otherwise, Eruption + Hyper Voice/EF go brrrr.
2. You can find some good teams in the links below, and in probably a couple days/weeks, these forums will have a list of sample teams:
Labmaus - Top Teams
Victory Road - Baltimore Regionals (scroll down to see teams)
CybertronVGC: M-Salamence video is great, some of the others are...more unique (but fun!); explains thought-process very well; highly recommend
JoeUX9: Great channel and the WINNER of the Baltimore Regionals
Justin Tang: Very chill and explains thought process behind moves/team-building/etc. very well
3. Nothing to say here except that Bo3/tournaments is slightly less lead reliant since you have access to your opponent's team sheets (so you can see if they have any wacky moves) and you have more time to adjust.
4. This kinda relates to RNG manipulation, but what isn't talked about a lot is mental fortitude. Being able to recover from a bad loss through methods like taking a walk is important so you don't go on tilt, objectively/calmly analyzing your games instead of blaming it on RNG, and not panicking after getting high on the ladder/making it to your first finals is really important.
As for practicing these skills, decision-making and leads can be learned best by watching VODs of great players. The Cybertron VGC and Justin Tang channels I linked above are great for beginners because they goes through their thought processes behind leads/decisions well. In addition, you could play games (if you're aiming to play in tournaments online or IRL, Bo3 on Showdown is best) and analyze them. Analyzing is basically asking yourself:
Pre-game:
1. Did I bring the right four Pokemon, if not, what could I have brought/dropped?
2. Did I lead the right two Pokemon, if not, what could I have led instead?
In-game:
3. Did I recognize when I could or could not make a safe play, if not, why?
4. When I had the chance, did I make a play that covered for all my opponent's options, if not, why?
5. When I couldn't make a safe play, did I reason out a little bit why I'm calling this prediction, if not, why?
Team:
6. Did I have the tools to deal with my opponent's team, if not, what can I change? (This can be Pokemon, moves, or strategies/gameplans)
CybertronVGC - How to Learn from Your Losses
The above video essentially says the same thing, and gives an example through an VOD review of one of Flats's games. (who you might now if you're in the shooter community)
For practicing teambuilding, you should first make sure your gameplay is fine before making your own teams. IMO, high ladder/tournament placing (master ball 3+/top cut) is a good sign you can start making your own. As for making your own, try slightly changing a team that you've played a while based on your preferences/meta calls. For example, I liked
this Mega Salamence team but didn't like that it was single-mega, had 5.5 physical attackers, etc. so I replaced Sneasler with Raichu and played a couple of Limitless tournaments with it and was happy with its performance. Then this weekend for the Global Challenge I took some inspiration from my old team, trading Rillaboom and Arcanine for Farigiraf and Volcarona (since I thought priority needed to be stopped and Volc's Flame Body/redirection was great in a format full of single-targeting physical attackers) and am currently doing well with it.
Sorry if this was a lot of info, so if all this went over your head, just remember to have fun! My advice is more for if you're serious about getting better, but if you just want to use your favorite mons and cool strategies and aren't concerned about rank or all that, definitely do so. This is a game after all; we play this for fun :)
