Three kinds of doors dominate my board, and two more get advertised across the wider market. Here is how each one actually opens, with the board's examples named.
The classic: your first deposits are matched at a percentage, in steps. Jackpot City runs four steps to C$1,600, Golden Tiger runs five to C$1,500. The trick with ladders is that every rung is optional and each has its own claim window. Climb the 100% rungs, skip the 20% filler.
A small fixed price for a bundle of spins at a progressive jackpot: $1 for 80 chances at Zodiac, $5 for 100 at Captain Cooks, C$10 for 150 at Yukon Gold. The entry price is honest and tiny. The wagering on whatever the chances pay is heavy, commonly around 200x. Buy the ticket for the ride and the jackpot shot, not for withdrawable cash.
Rarest breed: something for signing up, before any deposit. Casino Classic is the one on my board. Whatever the terms say, your cost of inspection is zero, which is the best price in the industry.
Two more doors show up across the wider market. The straight match is one deposit, one match, no ladder; a simple shape that says nothing about the price, because plenty of straight matches carry wagering of 40x, 50x or worse. The bet refund is a sportsbook special: lose your first wager and the stake comes back as a free bet, usually with light or no wagering on the free bet itself. Whatever the shape, the same five numbers below decide whether it is a deal.
Full worked maths lives in Wagering Requirements, Decoded.