I personally find that the only $$ gachas that may be worth it (aka, not a total scam) are 1) Miracle Tickets, priced at $50, which let you choose any 1 Kamihime (bar the limited-time ones) released before... & 2) the SSR Kamihime release weapon guaranteed gachas (usually priced at $50, though they've dropped them to $30 on certain occasions). I guess depending on how much you want to whale, you can also go for the SSR-eido guaranteed gachas or the SSR-any guaranteed ones.

Keep in mind that from your starting point, you'll be behind in terms of competitiveness or clearing the most difficult content for quite awhile until you build up your grids. Unless you mega-whale and just buy your weapon grids from the gachas, like some do. But for the most part, if you're smart about your grid building and invest time into them, eventually (months to a year) it's possible to get to the point where you can compete against whales, without actually spending (granted you'd still a need a bit of RNG luck throughout that time).

As for starter tips, the biggest one would probably be: if your current starting account doesn't have a good roll of SSRs from the starter 6K Jewels the game gives you, just make a new account and keep re-rolling until you get something worth sticking with. Refer to the re-rolling thread linked on these forums for more info regarding that. Good luck.