How many nights a commuter needs in base on reserve depends on how much you are flying. For me personally it has varied from none out of pocket to maybe 8. You can research crashpads online if that interests you.

12 hour long call reserve exists but there are only about 2 lines in each base and position so it can go fairly senior. You won't get airport standby every day unless you bid for it or you happen to be at the very bottom of the reserve list all month long. You will start with an 0400-1600 reserve period with a 2 hour call out and some of those shifts will be converted to airport standby depending on your relative seniority and the company's need. Many senior reserve pilots will find themselves on airport standby occasionally depending on the base.

Reserve schedules are typically 4 or 5 reserve days in a row followed by 3 days off. How quickly you move up the reserve list or hold a line is going to depend on what point in the hiring wave you are in. You need pilots coming into your base below you to boost your seniority. Trips are something else entirely. On your reserve day you might be assigned a 4-day trip, a round trip, a standby shift, or you might not be called at all. You might start with an overnight and find it extended into a 5-day trip. How much you fly on reserve depends on your base and relative seniority. I think the 4 am reserve period is more likely to get round trips and 10 am reserve is more likely to get overnights. You will have the ability to bid for any open flying the next day.