Hi, I got #1 at Vale of Eternity through careful practice and study. Always reviewing games and looking to get better so I can provide a decent method. One thing that took me from being one of the best, to #1 player was quite likely the fact that I created a strategy wiki site for the game and wrote over 10000 words of strategy articles for the game. By actively thinking about the game enough to write it out and setting up the game info pages I was able to memorize all the cards and really think hard about card interactions. This is not a recommendation to you, but an example about how regularly thinking about the game can make you play quite a bit better.
First off, becoming very good at board games will be much easier for certain personality types and professions. Expect the top players in many games to be highly analytical, logical, strong at mental calculations with professions in STEM, computer science, or data analysis, or finance. These type of players often fall into the "good at games" type of player who can learn a game very quickly and immediately starts the game for optimal plays and patterns, good efficiency, value of relative resources, resource management all upon learning the game. They can often outplay and win against their more casual friends that have played a game over a dozen times on their second playthrough, sometimes even first. Everyone has a different starting point and expect the top players to have already started relatively high relative to their game count. Some players start a lot lower, no judgement.
What to do:
1) Play regularly, but don't grind out games endlessly. Take your time with each game and really focus on what's happening in the game. Go back and look at the game review and look for key decisions. Maybe watch from opponent's perspective to see hidden cards. Number of games and amount of practice doesn't matter. The QUALITY of practice matters a lot more. If number of games was all the mattered there wouldn't be 100-199 Elo players with over 1000 games played, but there is.
2) Find good players, play them, chat with them, befriend them. Figure out how and where the good players are playing and try to join them. This could be arena or tournaments, real-time or turn based. Good players are usually friendly and helpful so just try reaching out. Sometimes you can just message them directly to play a game or ask a simple strategy question. I did this very early on when leaning Vale of Eternity and it worked well. Now I have a bunch of strong players as friends and we all play in tournaments regularly.
Even better than online friends is having strong gamer friends in real life to play the game with and discuss strategy. I played at most 20 games IRL with a strong gaming friend before joining BGA and we learned to play the game pretty good on our own and would discuss specific cards and strategies often. When I joined BGA I immediately jumped to over 300 Elo because I already understood the game quite well. From there I would try and befriend 400+ Elo players on BGA to chat about cards and play games. I even organized tournaments and invited all the top players from leaderboards to get some good competition. If you perform well in tournaments you get rewarded with more games against better players!
3) Study all the game pieces, know all the rule interactions and little details. This means knowing the contents of any decks, tiles etc. Level of detail required required may vary. For example in Faraway, I know the relative distribution of the 4 resources in the deck, but don't know all ~100 cards exactly. In Vale of Eternity I know all 70/70 cards from memory perfectly so I can literally "look at the deck" in my head, swipe through them 1 by 1.
Also know all rule interactions so you avoid making preventable mistakes. No need to learn from experience if you can learn it from study.
4) really focus on learning strategy and tactics. The basics for most games should be easy to figure out by seeing what works and doesn't. You need to always be taking mental notes on how good a current scenario is and then what the game will likely look like later on. Can you identify strong early game setups and make them yourself?
5) Once you are good enough to focus on yourself and play well for yourself, the next step is to consider playing from your opponent's perspective, what they want to do and consider efficient ways to block them or slow them down that provide a net benefit to you. Try to really get in their hand and think about what they want to do on their turn. In Vale of Eternity I can do this very well. The game has open drafting so I keep notes of everyone's hand and know what all the cards do so I often have perfect information about their game state and put myself into their perspective about what they want. If I identify that they are looking for specific cards, or have an imbalance in their resources (currency, cards, space on board, or point scoring) I will often be able to cut them off from whatever resource they need the most, punishing them for getting imbalanced. So I might either cut them off of scoring cards to make their currency useless or I will cut them off of currency so they can't summon their cards to score, depending on the scenario. I can play from their perspective because playing for myself is easy enough now.
6) plan multiple moves in advance whenever possible. How to do this varies from game to game.
7) look at other strategy resources such as through google search, reddit, or Board Game Geek to see what they say. If you really get nothing, create a new post asking for basic strategy somewhere BGA or Reddit and see what happens.
I wouldn't look for game replays on BGA with enough comments and strategy to guide you. That's going to be very rare. Just play a game against a good player and have you 2 talk a bunch during the game. Much more straightforward.