I started with a kit, Liquid Barn's. I wouldn't recommend that kit simply because the only flavors available for it are LBs proprietary ones, and there are very few published recipes for them. Creating your own recipes is like the next level after simply learning the mechanics of mixing, so the LB kit is sort of forcing you into a higher skill set you may not be ready for. Which is not to say their flavors are bad! In fact some are very good, but as a new DIYer you'd be better off starting out by picking some recipes that sound good to you and then choosing those flavors with your kit.
The Nicotine River link you posted will allow you to do that. It's a good looking kit at a great price, 15 flavors of your choice to start you off + all the other stuff for 50 bucks is a great deal. I wish it had been available when I started out. Chasing down all that stuff from various sources is going to take time and $hipping fees, why not get it once and be done with it? Once it's in your hands, you'll be able to figure out which direction you want to go.
Many folks will tell you "You don't need a kit, there's stuff in there you'll never use". They are speaking from their own mixing preferences. You don't yet have a preference, and a kit is a logical way to get quickly on the road to developing one. My recommendation would be to search out some recipes you want to make, pick up that Nic River kit with those flavors, and also pick up an LB501 scale. With that gear, you'll be good to go in any direction you want, for well under a hundred bucks.
