I've spent MANY hours on YouTube watching so many
BAD/USELESS videos on the Ender 3. The one posted above by
w1lp3 is without question the best I've seen. I wish I had found this BEFORE I built mine. The section on adjusting the roller wheels would have save me lots of frustration. PAY PARTICULAR ATTENTION TO THAT SECTION! Virtually all of my wheels were adjusted too tight from the factory. 4 wheels were even flat spotted from being over tight causing all kinds of print problems for me due to the flat spots. I ordered replacement wheels from Amazon. Replaced a total of four and adjusted ALL wheels to a realistic preload. Made all the difference in my print quality. I'm still learning the ropes and am getting my printer closer and closer everyday to where it needs to be for exact prints thanks to all the help I'm getting here and on Thingiverse.
Keep at it. It looks like a lot of adjusting is needed to get everything set to your individual printer/designs but it really is worth it. It won't happen overnight but it really is a fun learning experience. Aside from the too tight wheels the unit has been trouble free for me other than making custom settings for the prints.
Remember to install Cura for your slicer. Join Thingiverse and the Thingiverse Ender 3 group. Install Pronterface for an easy way to update printer settings. Give TinkerCad a serious look for designing items. I "learned" it much faster than I expected! It's all very mind boggling at first but many people have been patient and helped me get this far. Kudos go out to all that have pitched in so far!
Joe