Congratulations on getting the bike and getting out for your first rides.
Paddywan wrote:my stamina only allows to me ride for 20 minutes or so in "bursts" of energy before my legs have completely turned to jello and i'm peddling around in one of the easier gears, but I suppose that will never change unless I keep myself committed to both my diet & activity.
I'm not entirely sure if I enjoy it or not yet, it sure is a hell of a lot of effort and work and for the moment I'm too busy being focused on the what's, why's, and hows as well as safely navigating traffic. Perhaps once I've stuck at this for a while longer, built up some muscle mass and become accustomed to the bike I can start to enjoy my travels rather than see them as a means to an end.
Those 'easier gears' are probably the ones you should be choosing in the first place and riding around most in. You will not get fitter more quickly or lose weight more quickly if you fall into the trap of thinking that you have to push or even batter yourself when you go out for a ride. There's probably a deep seated belief in many of us that getting fit and losing weight shouldn't be easy and that we must suffer in order to 'earn' improvements in fitness. That's codswallop.
Whereas Chris Froome probably does have to stick to very precise training programmes, which will include pushing himself to the limit on set occasions, all in order to achieve even marginal improvements in fitness and weight loss, you weigh so much that you will find it impossible not to lose weight and get fitter if you keep riding your bike every day or so.
Just focus on building up your stamina. Not stamina to ride above a certain speed or to push a certain gear, just the stamina to ride for longer periods. To begin with it doesn't even matter how far you can go. If you can build up to riding in a very easy gear for maybe an hour, possibly with some rest breaks in between to admire the views, you will gain far more benefit than going hard for just 10 or 20 minutes.
Make sure you are comfortable on the bike. Pain or discomfort are your biggest enemies: they will discourage you from riding.
Make sure also that you enjoy it - that is what will motivate you to keep doing it.
If you keep doing it, you will find that you are losing weight and getting faster without even realising it, i.e. your fitness will improve such that you find that you are still riding in an easy gear, but it is a higher gear than the one you used when you started.
You will probably find that you get more used to the traffic, but even so spending time researching routes that use quieter roads and off road tracks is usually well worth it (and the scenery is usually much nicer). What most new cyclists don't know is that most experienced cyclists tend to have routes that they will always use to get out of town, and those routes will often not be obvious, because they will link up minor roads, cycle tracks and bridleways to avoid the busier roads. So it might repay you to see where other cyclists ride, to go out exploring your local area (on your bike obviously) to look for new routes, and to look at a map, especially any intended for cyclists, e.g. https://betterbybike.info/maps-and-rides/regional-cycle-maps