The items you listed are available any where.
I would ride it for a while and see if you need the mods before spending the cash.
Mods are usually added because you want to improve the performance of the bike, or in some cases the look.
Phone holder- When I use the phone as a navigator, not for conversations
Custom saddle- That's a big expense, be sure your current saddle does not suit you first
Mud guards- Those can be had for little and are useful if you ride in the rain or muddy conditions
Tyres- If your current tyres are not suited to the surface you ride or are worn out...