It is good to go for single games instead of accumulating bet, that is one if the right thing to do while gambling because one game can cause an accumulated bet to be lost. But the mistake I see is that you are going for underdog, because they are having more odds and you think they can win, or draw. So far matches can be won, drawn or lost, that creates more ways to lose. You selected some to draw where it is possible that the underdog might lose or win. I will advice you to just go for clubs you think that would win if a strong club is playing with an underdog. Never take gambling that serious.
I want to correct what you said, maybe in casino gambling. we better not take it seriously. which means, we just play for fun.
IMO, sports betting can be taken seriously especially football. but with conditions, must have sufficient knowledge and experience of the teams that will compete. in this case, I'm referring to the big leagues. as you said, choosing a single bet is the most ideal thing than gathering several teams and then entering a parlay bet slip. single bets are more promising for victory, because we only bet on one match and this is obviously very different from the parlay option.
IMO, the problem is that most gamblers want the highest profit offered by the dealer. as in this case, the Op. the most fun thing about choosing an underdog team is because the odds that the dealer gives are very high. however, in fact if we refer to statistics, teams, odds, then it's only natural that the bookie gives big odds.
because most likely, the underdog team will lose and this is the simple logic. however, it could happen otherwise the team that is not the seed will win. However, it is important to remember that we must involve analysis, knowledge and all the latest information regarding the match. in essence we as gamblers must use logic when we want to bet, principles of knowledge and analysis are needed to be considered especially in parlay options. ideally, if you want to bet on a parlay, 3 teams are enough for me. the chances that we have too, are bigger than choosing many matches.