Batu caves, translated blandly as stone caves, is one of the farther but also easiest to visit top tourist spots from Sentral Station and very affordable at around $1 per way. It’s a large complex with multiple caves, some of which are pay for entry, but the main attraction, marked by a huge Hindu statue and stairs is free to explore. To maximize your time, it’s worthwhile to take a left halfway up the stairs and sign up/pay for the Dark Cave tour, then continue up the main stairs to explore the free parts of the cave instead of waiting an hour in line for the tour. Don’t forget to hydrate with a fresh coconut! This half day excursion works well with a return trip to Pasar Malam Jalan night market where you can shop for souvenirs and dinner.
A great way to maximize a day trip by public transit is to start at a farther station near some attractions, but return to a different station that is close to a night market or attraction near to your billeting. This way you can end the day with a nice meal and drinks while feeling safe that you’re near home.