I would say endos, bunnyhops, and 180 rollbacks are several great skills to have.
There is no 'should' in a sport called freestyle. There are natural steps to progression in tricks, but there are so many variations to tricks that you really can just learn the one trick and nothing else, then that will brach sideways into tricks that you didn't expect to learn. I know a guy who could do hitchhikers but couldn't do almost any other flatland trick. He's got a lot more tricks now, but he doesn't have a lot of the 'basics' that he could have.
Just go to www.bmxtrix.com -> how-to -> flatland or street/dirt/vert and pick what looks fun. Keep in mind MOST of the easier stuff is towards the top of the list. But, pick what is fun and don't worry about 'should'.
Fork glide is a fork wheelie with both wheels on the ground. So you do the first 180 like you do for a fire hydrant, but intead of lifting the back end, you leave the back end on the ground and just roll backwards. Pull down on the front tire with your foot to get some speed.
Also note, both fork glide and fork wheelie, you want to be able to do either holding the seat with one hand (either hand) and you also want to be able to do both tricks with both hands on the handlebars at the same time.
Looks pretty nice, my bike is fine i just need to fix my brakes... they are crap. Oh and BMXTRIX i can do some of the fork wheelie, i can twist my body 180 degrees so im on the front pegs and my handlebars are backwards but my right foot that is supposed to kick the tire goes to the ground and i cant kick the tire b/c it stops you so fast.