Yo. Rerolling is for pussies anyway so if you are just starting it will not affect you at all. Nowadays most of the meta decks are fairly cheap anyway so just by progressing you will get what you need. And even if you have cctg exp, with less than two weeks left you will not try to get competitive in the first season of rotation mode. Take your time and enjoy the game, you should progress and increase your lib naturally. Reroll in encourages net decking and playing for keeps from the get go, ruining the fun for newcomers in the process. I did not reroll, I did not net deck till master ( too be fair I did not net deck after either, but by this point you know the meta and prob can put all of the decks on the net yourself) and I have 10 + years of experience with that stuff. Why restrict yourself of the intuitive/creative aspect right from the start. Screw guides, just have fun at least for first few weeks and figure that stuff on your own.
I'm not 100% sure telling you not to reroll is the right answer
The right answer is "do what you think is fun"
Rerolling is of course boring as hell, but maybe there is a specific card/deck/archetype/class you think is very fun and you'd like to play from the start.
What I personally did was rerolling just a few times. I found a few decent things and, among them, a copy of a Legendary I thought was cool and I started building from that.
Still, the game is very generous and if you play with even something remotely resembling some kind of consistency, you'll eventually build a few competitive decks without spending money.