This is the network on this site and i have two multi-sites apart from the main one, what i want to know that, can i create this many multi-sites, without the network crashing or having too much errors or the database itself would crash because of the too much data?
There really isn't an answer to this. Yes, you can create 300 subdomain multisites with WordPress. But questions about the network crashing or database issues really depend on what kind of hosting you have (i.e., shared, VPS, dedicated) and how much memory and bandwidth you are paying for. These are issues you need to take up with your host.– Kenneth OdleApr 21, 2017 at 12:24
300 sites within a multisite shouldn't be a problem by itself. Just be aware that things scale out quickly when you are operating that many sites. In particular, the number of posts will grow fast, and depending on the type of site, the traffic can grow fast.
300 empty sites with no traffic can be run on any shared hosting, but as the post count and traffic grows, you'll want to look into more robust hosting options.