I will second several of the points made already...
It's always good to have some DME (extra light, or light) on hand in case you really miss your target, and really want the higher gravity. I didn't have that for my first AG batch, and while the OG was high enough for a style, it wasn't enough to hit my target style. You can also use the DME on hand for making yeast starters (also a good idea)... So it's not like it will not be used at all. For the first few batches have 1-3#'s of DME on hand, just in case.
It will take at least a few batches to figure out your system efficiency. I'm still in that stage myself. In my first AG brew, I really screwed the mash up, so my efficiency was pitiful. With my second, I went back to a more traditional BIAB method. I got just over 81% efficiency there. I'm debating going with a full batch size mash for the next one (no sparge) to see how that goes. I got a couple of holes in my grain bag during yesterday's brewing (caught on the thermometer's shield, and got two small holes in it) so I need to get a couple more grain bags (want to have one 'spare' just in case)...
Couple of other things that will help your brewing... Get a wort chiller, if you don't already have one. Or, if you're so inclined, make one. I made an IC with 20' of 3/8" copper tubing. I have about 19' worth in the wort come time to use it. I'm able to get the wort from boiling to <70F in under 15 minutes using cold tap water.
Keep something else in mind... If you're brewing on the stove top now, you'll probably want to shift to outside as soon as it's not bitter cold out. Get a high enough BTU propane burner, and a couple of tanks (always good to have a full one in reserve) and you'll be happy. I'm planning on doing that come spring time, getting a larger pot so that I can do full boil volume (post mash) mashing (or no sparge)...
I would also suggest getting a good thermometer that can handle the long boil times. I thought I had one to use (a candy/oil thermometer) until yesterday's brewing... It started going weird on me partially through the boil time. It pretty much died, and gave false readings, during my cool-down period. Before my next brewing, I'll need to get a reliable thermometer to use, that I can either just leave in the pot, or have a probe that will be good being inside the wort. I expect to be brewing in another 2-4 weeks, so I'll have to get a new thermometer within that time frame. Keep in mind, I only used the thermometer for six brews.