You've gotten some great advice. I'm actually a big fan of the RKC plank. Here's why: It takes at most a couple of minutes to get a few sets in with rest between sets. (If you can hold it for longer than 15 seconds, you simply aren't doing it intensely enough!) That means it's also easy to throw into a workout at the beginning to prime your core to be more involved on successive lifts, so that your core stays indirectly involved while you work on other lifts. That'll cascade into hypertrophy benefits over time while you focus on the big lifts, which should be the bulk of your training. In other words, it'll help you to workout your abs without taking time away from other lifts. And it will help those lifts get stronger in the meantime.
If you got any other questions, please post them. I started lifting at 6'!", 145 lbs. Not as light as where you're starting, but I can relate to some of the gym struggles of being both light and tall. My first post on here was asking about how to do cable pulls without it lifting me off the ground!