You can buy a SIM card for about 65,999.24 IDR, which includes 2 GB of data plan. You can choose from 7 telecoms: 3 (Tri), Bolt, IM3 Ooredoo, Net1, Smartfren, Telkomsel or XL Axiata.
Indonesia uses GSM mobile networks GSM 1800.
If you don't want to buy SIM card in Indonesia upon arrival, make sure to check the roaming charges with your telecom provider before your departure so there are no surprises when you return home.