This depends on whether you're playing online or offline. Online casino games offer more flexibility and usually a wider selection of games too.
In online casinos, you can start betting as low as:
Roulette: 10c on individual numbers or outside bets
Blackjack: 10c per hand
Slots: 1c per pay-line
In brick-and-mortar casinos, there are human dealers operating the table games, and those people need to get paid. That's why the minimum bets can be quite high compared to the online casino. In a land-based casino, expect to bet at least:
Roulette: C$1 on individual numbers, C$5 on outside bets
Blackjack: C$5 per hand
Slots: 1c per pay-line