My first project was "Game Like", i offered to make a database and website for my brothers phone repair company and they wanted to track everything and reward their employees with Achievements and xp for fixing stuff and helping customers out.
I can say without a doubt.. Get a pad of paper and write out Everything! i thought it was going to be easy. currently we are tracking around
(around)74 models in each manufacturer
24 Part Categories for each model
(around)100 Items in each category
with around 200 employees online between 9AM and 7PM. they have a chat open during those hours as well between all of them.
I started this when i was 16.. I am now 18 and we are approaching the final release of the new system. (we have gone through about 2-3 Massive Revisions) and i have posts on this website back when i first started this project lol. (Thanks for all the help back then Nogdog )
I just say this all to give you an idea of what my experience is.
Have an idea what your host is going to be, we have around 200 users and are using a 300$ a month dedicated server. not to bad considering how much money it has made us (and we like the extra memory lol).
Make your own framework if you know basic php. Include simple functions like one to verify if the user is logged in and ones to send Queries etc...
Learn PDO or MYSQLi for sending stuff to a database in a nice secure way (and than include it in your framework as stated above).
Lean on a Secure Tested Framework if your really afraid! When i first started on my brothers website i used PHPBB3's login to support my website and it worked wonderfully because it had an included forum, The one major downside is you have to work with someone else's project and that can be a pain. it is well documented and there are thousands of mods to help you learn how to modify it though.
I have since made my own full framework and security measures and left PHPBB in the dust, but only because i am now confident and have people to test stuff for me.
Choose a data delivery method, redirecting people to a new page for every little thing is a bit sluggish for games, so looking into Ajax is pretty much a must. the more Dynamic your website the better, And the more complicated.
Get ready to master optimization, games are very content heavy. if you want anyone to hang around you better learn to manage that either by pre-loading everything, making massive sprites, and reduce the amount of calls the system has to make to get from point A to B. (and yes this applies to just a text based game, You will be juggling a lot of Data and even text can begin to amass)
And my last bit of advice, if you are actually going to make it live.. Get ready to be overwhelmed with bugs when you start to let people in and be ready to manage bug abusers. Make tools to help you ban people and revert stats to a previous date etc...
I could literally go on for hours but i doubt you would read the entire thing.
So i hope you Enjoy this short bit and i wish you the best of luck!