I will not write about interlinking because I do not have much info. But I have some questions:
1. Will these 50 (or 300) blogs be standalone websites? In another words, will they be created to support your main sites or will they be built upon well-chosen niches?
2. I do not know why do you think about subdomains? How can you interlink subdomains? Don't you think it is not better than using seperate domain names? And also (maybe) it should be risky.
3. For C Class IP hosting, go for chilledhost. They have a special promo for seo hosting. You can have a network hosting for a year cheaper than one month's price of seohosting. Promo code CLIENT and it gives 55% discount. I use their service and happy up to now.
There are two ways to do this:
1) Just get different domains from different hosting companies, which are almost by definition on separate IPs, but you should check to make sure. Put who you got them from, login info, and any other particulars in a spreadsheet so you don't forget what you have done. Ecrypt that file. Don't necessarily use the same domain registrar for each and don't use the same domain ownership info for each. Use subdomains instead of all unique domains. You don't really need each domain on a separate IP. What you need is unique content the blogs. Use more than one method to blog. They don't all have to be Wordpress. Even if they are, they don't all have to have exactly the same set of plugins or configuration. Get links to the blogs. Well constructed link pyramids still work well.
2) Get your different c-class IP hosting from seohosting.com. They are pretty good. You will have to learn whm, which is how they manage the IPs and domains, and you will have a separate cPanel for each domain. The have a lot of tutorials that explain it, and their live chat help is quite good in my opinion. All of the other tips above still apply.
One of the most misleading advice that I have seen here. And unfortunately OP thanked him. Let's examine:
1- "Just get different domains from different hosting companies" NEVER EVER DO THAT. Never buy your domains from hosting companies even they give it for free. (Or use those domains just to support your main site. But be ready to forget them after a year or after a problem with the hosting company). Buy your domains from
--- Goddady
--- Netfirms (now $4.95 for .coms)
--- namecheap
--- dotster
--- name
--- and the other domain registrars.
2- Sorry. I will not go on. Because everything he wrote is a crap nothing else. No need to use such an excell sheet. (but OK for other processes). Forget everything he wrote. WP is good enough for all your blogs. Are you crazy to learn 20-30 scripts? (like joomla, Moodle, mambo, serendipity, lifetype, nucleus...)
3- Last but not least, seohosting.com is the last option get different IPs. It is too much expensive. Rather, use chilledhost, or find Josh.w36 (here on BHW) giving c-class IPs and hosting for a reasonal amount of money.