Some people may think getting high up in the highscores is something that is impossible unless you absolutely no-life the crap out of the game. For those of you that want to compete in them but never got to due to thinking you're 'too late', I'm here to show you the contrary.
First off, probably the most important thing to competing in the highscores is getting maxed. This isn't something you do all that quickly, but plenty of people have pulled it off in a few months. As I'm writing this we currently have 177 maxed players, so getting maxed would already put you in the top 200 players.
With construction coming out soon, there will be another skill to train to get maxed. The people that are inactive are likely to drop down in the highscores, and it's a good opportunity for you to start getting a higher rank.
Combat exp is mostly regarded as the easiest exp to gain by people that are in the higher pages of the highscores. It might be a little more expensive to train ranged or magic but you could also do this with pest control. There are 6 combat skills, the total exp you would get from them is 1.5b.
To add to that, if you're maxed you should at least have 13m and 34k exp in every other available skill. That's 16 skills (or 17 with construction). Combined with having 250m in every combat skill that would put you at a total of at least 1.7b exp. This would currently get you a spot on the front page of the overall highscores.
Tl;dr: Front page highscores are by far not as far off as people may think. Competing is definitely doable.