As someone who has built up a small following on YouTube, I'll give you the following advice (that others haven't already repeated):
a) First mistake is thinking of YouTube as a career, which you've said so in the first sentence. Until you are
eligible to be part of the YouTube partner program (where you can start making $$) and garner over 100k+ subs and 10k+ views on every single video, don't think of YouTube as a career. It's the
fastest way to get burnt out. Instead, think of it as a hobby/passion, you upload something and if it does well, great. If it flops, then never mind, at least you had fun making it.
b) Don't expect immediate success. This video that I posted a while back, got 171 views within the first 24 hrs. Look at it now. The algorithm works in mysterious ways.
c) Unlike others, I'd argue that SEO & tags (while important), it's not as important as you may think. Video tags itself has a limited impact on discoverability (YouTube literally says that when you upload via the creator studio). Hashtags are okay. From my experience, it doesn't do much but any discoverability is better than none so I use them for every video but I would include them in the video description but not the title because it makes the title seem really long and spammy which may result in some viewers not even clicking on the video to watch.
I try to have good SEO for every single video I post and truth be told, sometimes it works but sometimes it doesn't. That's why I believe while it's good to have, it doesn't play a big role in getting a viral video. Good thumbnails, a video description that accurately describes your video and audience retention are all more important factors.
