just got back from 6 days at Bandung and 3 days at Jakarta trip. From my experience,

for booking train to and from Jakarta and Bandung, use Traveloka website or app to purchase.

for prepaid SIM card, get your Supir to buy it for you so that you don't have to register your name and avoid having your info being misused and also avoid being scammed. Our supir got us the SIMPATI 5GB card for 50k rupiah. We inquired at an outlet for the same pack and were quoted 90k rupiah.  Telkom Indosel coverage is terrific at Bandung and Jakarta. There's 4G coverage everywhere except when we were at Sepa Island Jakarta where we got 3G+ coverage. Even at Tangkuban Perahu and Kawah Putih, there was 4G coverage.

for clothe shopping, as some forummers pointed out, some brands like Polo Ralph Lauren and Burberry aren't genuine including those sold at Rumah Mode.
shopping at pasar baru bandung was crazy with hundreds of outlets but prices can be high compared with those at pasar baru jakarta. we found batik shirts at much cheaper price at pasar baru jakarta. but if it's variety you're after, then pasar baru bandung is the place to go to especially for Muslim clothing and textile.

for leather shoe and leather products, shopping at the infamous Cibaduyut area was a huge disappointment. Shops were practically selling the same mass produced fakes or imitation brands, and many were not made from genuine leather and were generally pricey. We stumbled on an in-house handmade leather shoe shop at Jalan Braga but the shoe prices start from about RM750 onwards. Then on our last day at Jakarta we discovered this Indonesian shoes brand, Buccheri, at pasar baru Jakarta which is claimed to be handmade and is made from calf leather. Discounted price was reasonable at about RM120 onwards.

for those who wish to go to Trans Studio, do take note of tiered entrance price. Monday to Thursday are the cheapest. followed by Friday. Sat and sunday are the priciest. For entry discount, purchase tickets from Traveloka. Tangkuban Perahu also have different entry price between weekday and weekend.