USe the bid option on peakmonsters when buying cards. Teh fact that most cheap cards are of the market near instantly is due to this bid option which gets filled automatically and is therefor much faster than any clicking by hand.
With the power problem there is literally no way besides invest some serious cash. The current cheapest power (common reward gold foils) costs about $0,04 per power which means: you need to invest $98 for Bronze I, $498 for Silver III, $1098 for Silver II, $2298 for Silver I.
Sure there is the option to rent cards to get the power but this makes literally no sense since you need to be lucky to and hit big at the reward cards at the end of the season to pay for the rent.
Sorry but there is literally no other way if you wanna make this fast. Invest the time or the money like in many things in live.