So you wanna start doin' some runs, eh? Well I got just the guide for your face.

The first thing you want to keep in mind is do NOT worry about your time for the first run. All you need to do is learn the motions and get into the groove of things.

To begin the run you create a NORMAL difficulty world. The splits should be started at the same time you hit escape to skip the little black screen at the beginning of the world. From here you want to pick up your starting items, next to them are dead bodies of a dog and a blue fly, theses corpses can drop items, the dog has a 50% chance to give you a horn and the fly has a 30% chance to give you a blue crystal, if you don't get these drops, don't worry about it.

Once you pick up your starting items make you way to the left, at this time you are looking for flowers of light that grow in water, you will need a total of 9 of these. 5 for the shotgun and 4 for the flashlight (the flashlight is not completely necessary though I highly recommend getting it). Once you have these dig up a few trees and put down your autobuilder. You want to make about 30 wood blocks (15 wood total) and use all of your scrap for iron; you also want to make the shotgun, this is very important throughout the run. As you are doing this, constantly be looking for coral and blue flies, you need a total of 5 coral and 5 blue crystals from the blue flies.

Once you have made your items you want to rush your way to the left until you reach the chasm and make a small bridge to allow yourself to shotgun jump to the other side and grab 5 red ferns MAKE SURE TO KILL AT LEAST 1 BAT. Once you get your ferns jump back across the chasm. Now you want to make your way to the mountain and go to the top, when you reach the top, get 7 white flowers and then descend the mountain. Now you want to farm red flies until you get 8 red crystals.

Night time. This is probably going to be the hardest part to get used to. In order to survive the night, you need to find a decently large pool of water and spend the night in here. The reason for this is because it allows for great maneuverability. throughout the night the fly enemies will gather at the top of the water and will be unable to fly down, while the bats make a slow flight in your direction, you want to use the shotgun to clear the bats and then kill the flies. This is not that hard to do, though you may die a few times while trying to learn this strategy.

Throughout the night you should have collected at least 15 radioactive blood. use this and 3 of the red crystals you got to make the autobuilder and miniaturizer mk3. Once you do that, make your way back to the chasm. make sure you have 5 red crystals remaining. Jump down the chasm until it gets dark and your only light is your flashlight, land on the side of the chasm using you shotgun so you dont die. now you need to get 10 aluminum, this is really easy to find, so you shouldnt have much trouble. With the aluminum, make the laser gun as it will be your best friend for the mad crab.Now that you have your laser gun, jump down the rest of the way into the chasm and make your way left, try not to get distracted by any enemies.

The Mad Crab can be very challenging if you don't use a few strategies for it. The first thing you need to do is clear out the initial enemies he spawns. Once all the enemies are dead, start shooting the mad crab and just keep going right, instead of moving your aim to hit any more enemies he spawns, line up the enemies with your shot so that you are constantly shooting the crab, this way he wont de-agro or start regenerating health. This will take a little time to get the hang of but once you do, it becomes second nature. simply kite the mad crab for about four minutes and he'll die. Split as soon as he collapses. 

This should be a good starting guide to get you used to running this game, the beginning of all the categories as of now are fairly similar to this, so you can use this to learn all the runs at once.

This is not the absolute fastest route currently, but this is definitely the route you should start with. Good luck and have fun with your runs.