On the contrary, there is nothing limited to top 100. You can reach diamond rank 5 and get the same token as someone on the top 100 leaderboard.

It is entirely possible for a very average player to reach Diamond rank within a week or two if you take 5-10 minutes of your time after every 3-4 games to critically think about what you personally did wrong during a loss and what you personally did well during a win (do not focus on other players' performance).

You can even use this forum (even though its mostly used for complaints) to ask for advice and people will be quite amenable to parting with some valuable information that could potentially help you increase your win rate.