(1) Baby Bouncer is very useful as it gives your young infant an alternative place to hang out other than his bed. The bouncing effect makes them feel comfortable. I have one that can rock and vibrate but the vibration is not necessary. You can buy a hanger of toys as add on, something to entertain the baby when he is awakes. Mine is from fisher price, cost about S$100. My friends got this for me as a gift.
(2) Tricycle is very useful if you have active toddler that like to go out but do not like to sit in the pram anymore. My son started to use it when he was about 10 months old. The beauty of this is that it has a post which you can steer to where you want to go, there is a basket for you to put the water bottle for the little one, there is a bar at the seat to prevent toddler from falling and you can remove the foot rest when the toddler is older where he can then paddle. I don't really care for the sun shade as it doesn't do much and block my view of the toddler. I bought this at Carrefour and paid about S$50 for it.
(3) Foam Mat is good for infant and toddler to hang out. It helps define the place where they can play so that toys will not be everywhere on the floor. It is safe for infant who is learning how to roll over. Kids like colorful thing and some mat can be a puzzle for them to play as well. The only thing is you need to assemble them back for them. For convenience purpose, you can buy the 2 feet wide but the 1 feet is more common and can make it more prevailing for kids. To make a 4 by 4 feet area, it cost around S$25.