I'm all about not having uber characters, and was just about to make a post about how to gimp a character for a more realistic and challenging runthrough
to keep your level cap at 30 do not get any DLCs -or- make sure you get Old World Blues which allows you to take the Logan's Loophole trait, capping your level at 30.
For weapons: limit yourself to standard versions with mods (like scopes, barrels, etc) and use no Unique version of weapons to even the playing field
For skills: read NO skill books! With an IN of 6 or higher you'll have plenty of skills, but not enough to max everything, forcing you to be strategic with where you allocate them
more later, enjoy!