sometimes some matches take a while to get ranked, i think it happens when somebody stays in game after the match is over, bcs hes afk or forgets about it. when you now play your next game and win it seems your ranking isnt increased at all.
the difference in ranking points you get depends on the peoples rank, the balance % and your total games played. When the balance is against you and you win you get more points. when you are the lowest rank in lobby and win you get more points. the lesser games you played the more volatile your rank is bcs the system isnt sure about your skill level yet. also you get more points in games with less players.
its basic statistics, the more often you repeat something the more stable is the result or smthng:P just play many different maps, map gen and tmm, this will make you truly better, not perfectioning your super tight gap bo