For years my sites were all in Hostgator shared hosting until about three years ago when my accounts kept on getting suspended for exceeding the allowable resources. My shared hosting then had a limit of 2GB disk space, 10GB monthly bandwidth and a couple of hundreds of RAM. Disk space and bandwidth were the lesser problems. My web host was complaining of my memory usage as a Drupal installation profile I used for a news site required a minimum 2GB of dedicated memory.
If your web sites do not require special server scripts, you may start with shared hosting and the market for this is huge, some providers even offering rock-bottom prices and extra bonus features. But not all of them are reliable on long term basis, so you have to choose your web hosting carefully. A convenient reference in this regard is Consumer Rankings which offer ranking for top hosting sites, web hosting price comparison and web hosting bandwidth comparison.
In addition, you can read reviews of top hosting sites and compare recorded uptime, ease of use and page loads. It is surprising also how add ons have increased dramatically. For less than 5$ a month, you can have over $200 worth of ads credits in Google, Bing/Yahoo and Facebook. Years back I given only $25 ads credit for Google Adsense. Some even offer advanced internet marketing tools.
It's also a curious thing that most shared hosting companies now offer unlimited disk space and unlimited bandwidth.
When I needed to install server-side scripts like Apache Solr Search and Varnish http accelerator, my next upgrade path was a Virtual Private Server (VPS). For a start, I chose a managed VPS which is bundled with cPanel control panel, the web host control panel that is easiest to use but, I would later learn, use up lots of memory.
Recently, I have dispensed with cPanel saving $10 a month and my VPS is now self managed. You also save at least $10 a month if your go for unmanaged VPS hosting. Moreover, cPanel has compatibility issue with Varnish. I now use the free versions of Virtualmin-Webmin as my control panel.
I have just recently started experimenting on cloud server web hosting with Rackspace and Amazon Web Services, which all things taken into account, cost you a monthly expense of $43 and $80 respectively.
