you can start right away, but there are some safety tips you need to follow, such as:
1) build links slowly and focus on quality rather than quantity, especially if your domain is new and doesn't have a track record of acquiring links.
Google are heavy into historical data, and as soon as they see a new domain getting 100s of links when it previously got none they (google) get suspicious and there are big chances that you get penalized / flagged in some way, which can make ranking in the future way harder for that domain.
Quality links (at least in the initial phase) can be considered any / all of these:
a) quality PBNs (backlinks on the homepage of quality sites)
b) quality guest posts (articles published on other people's sites that are relevant to your site, and those sites also need to be in good standing with google)
c) quality niche edits (links inserted into aged and ranking articles on someone else's site, and those articles need to have authority and traffic, otherwise the niche edit will be useless)
d) editorial links (I don't know what these are, and I always mistake them for niche edits, but apparently they're their own thing, so look them up as apparently they're very important nowadays)
e) .edu blog posts / . gov links (self-explanatory, but basically blog posts on sites that belong to educational institutions like Universities / colleges, schools, etc... basically any site that ends in .edu or .gov is valuable as long as it's not a redirect / auto-approve comment, and has some content around it)
f) profile links (ie. links inside of your profile on big authority sites like Adobe, Issuu, Soundcloud, Author.me, etc... there are literally 100s of such sites, so you'll have a lot of sites to get profile links from, just make sure you don't get 100s of them at once, as I said in the beginning, or else you might raise flags)
g) topic-related links from specialty / niche forums, podcasting sites, online directories (these are particularly good if you're doing local SEO and find an online local directory that's very popular, a link from this directory - even if its authority is low - can be good for building local awareness and acquiring real, quality traffic, which google will see and might consider towards improving your trust signals and / or rankings)
2) probably optional, but I would still say to try and get most of the backlinks to the homepage initially, and - as time goes on and some of your other pages get some traffic - you can start building links to these pages too as the traffic would justify the acquiring of backlinks to these pages, which should - in theory - make these pages safe from link building-related penalties from google. In theory, though because only google knows what will happen in practice
3) last but not least, the 3rd important tip I can give about link building is to keep your anchor texts safe. Initially (especially if you build links to the homepage), your best bet is to use branded anchors as much as you can (just not 100% of the time lol, that's a dead giveaway that you're a link builder and google hates it), and mix some other types in, every now and then, such as generic anchors or naked URLs.
There are probably more tips I could give, but I'm not going to type it all here, so I will instead point you towards 2 very good guides on link building, give them a read when you have time:
https://www.blackhatworld.com/seo/guide-how-many-links-per-day-week-or-month-should-i-build.1502403/
https://www.blackhatworld.com/seo/guide-why-are-my-backlinks-not-working.1679105/
HTH
