I will add some of my thoughts here as well.
When I first got into brewing I wanted to do ALL of the things that the best homebrewers do, including harvesting and re-pitching yeast.
This may be something that you want to do, and may derive more enjoyment from the hobby doing it.
For me I found that it consumed a lot of time, and created a lot of extra work with additional cleaning, sanitizing, etc.
After a few months of doing this, I sold all of my equipment I had for this, stir plate, flasks etc.
I am quite happy to pitch new dry yeast in every batch, the added cost is well worth the time and energy saved for me.
Has my beer quality suffered for this? No, in fact removing all of those variables allowed me to focus more on my process.
My beer quality improved significantly, not because of yeast, but because of refining and perfecting my process.
A few things about dry yeast
The quality of dry yeast is at least equal to liquid yeast (or harvested yeast).
I would go so far as to say that it may even be superior in some ways.
One significant advantage of dry yeast is that you don't need to worry about oxygenating your wort like you do with liquid (or harvested yeast).
You can direct pitch dry yeast without rehydrating it into wort up to 1063.
Dry yeast is very stable, and can be kept in your fridge for many months.
You don't need to worry about when to get a starter going so it will be ready for brew day.
You can also have several yeast varieties on hand ready to go in tidy little packages, so handy!
The available varieties of dry yeast also continues to expand.
As far as beer quality goes, I hate to brag but my friends and family "can't believe I brewed that" most of the time.
I don't mean to discourage you from harvesting yeast for reuse, but I would highly recommend that you save this added process for later.
Concentrate on becoming a brewer, then work on becoming a scientist later.
Cheers, and welcome to Brewers Friend!