Well.. if the goal is just the occasional beach ride then it may fit the bill. Sort of like a boardwalk cruiser for sand. No one expects high performance.
Before looking at brakes I would ask if they are up to the job as is. If so hold off at least until they wear out the pads. At that time look at some better quality pads as they probably came with low end ones. Some people want a better overall system but if you are just doing the beach occasionally the Tektro's are probably fine for now.
A good swap is the saddle if it is uncomfortable. I say this because the saddle can travel from bike to bike so it is an investment that doesn't stay with the bike. Keep the original in case you sell it. The same reasoning can be applied if it has crappy pedals.
One reason people up grade is to lighten the bike. Without knowing the specifics I would look at the seat post and bars to see if they are steel or Aluminum. Not a big investment to swap either. I would also take off the kickstand.
The rims are already drilled so the next step is lighter tires but that is a bigger cost so again, maybe wait until you wear the originals out. At that time you might read up on tubeless to save a little more weight.
The other upgrade I see that may make a difference is the derailers and shift levers if the drivetrain is clunky and they are low end Shimano. An upgrade to mid grade components could make for smoother shifting.
Other than that, there's not much else to do.
Last edited by Happy Feet; 09-18-19 at 11:06 PM.