Women's Cosmic Down 20 (Prior Year)

Check out the Kelty Cosmic 40 - packs down to about the size of a nalgene, costs around $170, and is a solid mummy bag that'll handle those 50 degree nights no problm.

Honestly for 50°F you don’t need anything fancy. A cheap 40° bag will be totally fine. I’d look at something like the kelty cosmic 40 sleeping bag or the TETON sports trailhead sleeping bag , both pretty affordable and solid starter bags. Also, since you’re a bigger guy, just make sure you grab the long/wide version if they offer it. Makes a big difference in comfort.

I don't know about temps. Just depends what you camp in. General wisdom is to get a bag rated for 10 degrees lower than expected, but Scouts can supplement with more layers in the winter. There is a bit of science and experience needed for that though. I do not recommend 2 bags. A winter bag works just fine in the summer. Just unzip it or just use a blanket if it'll be warm. For any bag, be sure to check the ISO Tested Comfort Rating. - Product names and descriptions are often misleading, even for the big name trusted brands. Kelty didn't provide their ISO Test rating on thier website but they did in response to my email to customer service. - Amazon bags are often unrated so I wouldn't trust them. Bags go on sale a lot. The best bag is often whatever is on sale. I bought bags for me and my kids at the REI outlet website. Hikerdirect.com for Scouts has good bags at good prices. Much of it is Alps Mountaineering, which is a good brand. The Kelty Cosmic line is often recommended as another good budget brand. Coleman still makes good stuff, finding the ratings can be a challenge though. I wouldn't trust anything but a known good brand (that is ISO rated) for winter. A scout won't know if they have a bad bag, they'll just hate cold camping and won't want to go again. Also, the sleeping pad definitely matters for cold weather.