Hello from California!

So I got my first bike ever a couple months ago, 2003 intruder VS800 (55k miles on the clock), and have some concerns hahaha. Sorry for being a newbie but I don’t know what sort of maintenance she’s had and would love for some advice! I’ve changed the oil, oil filter, and spark plugs and she seems happy, but as far as maintaining and trying to make it last as long as possible what else should I consider replacing or fixing to ensure she rides for another 50k? Thanks much for your time and ride safe!

Hello and 

Hello and welcome nice bike and countryside   more of what you have just done at regular intervals per the maintenance schedule. Should keep her sweet ride and enjoy

Welcome to the club & forum, maybe you should get a service manual, hardcopy or digital and follow the maintenance schedule you find there. 
It might look something like this:

https://www.manualslib.com/manual/1042330/Suzuki-Vl800.html?page=545

as usual, Google is your friend...
Best times two wheels down.

Ser...

I have had my 2003 since 2005.  The hardest thing for me was adjusting the valves, mostly because some of them are hard to get to.  The manual I have recommends adjusting them every 4,000 miles, but they can probably go longer.  My philosophy is "loose valves are happy valves."  I can hear them clicking when I rev the engine and that's fine.
    If you go on long rides you will want a mustang seat or similar for comfort.  I put in irridium spark plugs which are good for a hundred thousand miles.  I had to give it a lot of choke to get it started on cold mornings, but I have drilled out the idle mixture screw covers and enriched it slightly for easier starting in the morning.  
    My bike has only 36,000 miles but it still runs like new.  Takes me and my wife over high mountain passes with no problems.  Good luck.
Arnold in Idaho