Yes to working weekends and holidays, because newbie. That said, it will depend on what base you're in and what season. In the summer, reserves get used a lot so the reserves go to junior pilots. The bottom of the seniority list can expect to sit reserve friday - monday the whole month, and only rarely get someone to trade their weekend line for your weekend reserve (it happens, just not all the time). In off seasons when reserves won't get called as often and in some bases where there seem to be lots of reserve availabililty and therefore less callouts, more senior pilots will bid reserve. But again, you'll still see weekend reserves go to the bottom of the seniority list.

Picking up out of open time is fairly easy, and there are a few ways to trade actual trips. Open time pickup is seniority based but first year pilots have a small advantage in that they can bid for open time trips at straight pay, and get paid second year rate. Straight pay bids have priority over premium open time bids, and some trips are great at premium rate but not so good at straight pay, so most pilots won't bid on those at straight pay. So a first year guy can pick those up reasonably easily.

Also, a handful of trips in open time have deadhead legs that might be to or from a place that is more convenient to you, so you can sometimes pick up a trip that deadheads from another domicile to an airport near you, or which ends in an overnight and a deadhead the next day. With those trips, you can sometimes call to get released from the deadheads and get paid for a 2-day trip where you actually only fly one or two legs before jumpseating home. The risk there is that the company can change up the trip once you're on it and that might kill off the good deal part, but sometimes you can get a whole lot of pay for one leg too. My best so far was about 10 TFP pay for a single leg, because to be a legal trip it required a deadhead from a domicile to begin and an overnight hotel stay before the DH back to domicile. I flew the leg, sat in the hotel 3 hours, and took an early jumpseat back home. 10 TFP at second year pay rate for about 7 hours time away from home, not too bad for a new guy.

I guess the simple answer is that SWA scheduling rules and current contract make it easy to fly more and hard to fly less. For a new guy trying to pick up extra, one of the biggest barriers is hitting maximum block limits because future reserve periods are counted as 6 hours block per day, and a reserve block usually gets you 96 TFP for the month up front. So it's hard to add to that if you're not careful managing block time. Picking up good short trips is sometimes a better idea than grabbing long trips even when the long trip pays well, because the extra block time in that long trip can prevent you from picking up anything at all for a while.