Is this optus internet fast enough for gaming?

https://www.optus.com.au/shop/broadband/naked/200-monthtomonth

This is the link, it is 200gb a month and 256kbps. I use it for gaming, streaming and downloading movies and games. I don't want high ping or lag when i'm playing games, we usually have 2 computers 3 iphones and an ipad connected at one time. Will i be lagging. I play games on computer like, "Garry's Mod, TF2 and xbox GTA5, COD" etc thanks

First lets go over a few of the details of the connection. The connection you will be provided will be ADSL2 or Cable based depending on the set-up available to you. Both of these technologies typically deliver fast speeds. Optus has, what is referred to, a data cap. This means that you are allowed to transfer a certain amount of data (in this case 250GB) over the period of 1 month. After you consume 250GB, your connection will be slowed down to 256kbps (which is incredibly slow).

For NBN, you can expect speeds up to 12Mbps down, 1Mbps up.
For Cable, you can expect speeds up to 40Mbps down, 20Mbps Up
For ADSL2+, you can expect speeds up to 20Mbps down, 1Mbps up.

Most games use a relatively low amount of data when uploading. A 1Mb up connection can usually handle most game servers, perfectly. (Some gamers have connections with 512kbps up and game just fine.) There are a few factors that go into gaming online though, speed is nearly transparent in comparison. Most of the issues attributed to online gaming are associated with latency (ping and jitter).

To get a better understanding of latency, I will explain what packets, ping, and jitter are.

Data is split up and transferred in segments called packets. Each packet, holds part of a whole. If a packet is lost (known as packet loss) the device receiving/client it will have to compensate for this loss, if it can, otherwise it may cause errors.
Ping measures the amount of time it takes for a packet of data to travel from your computer, to the server, and back.
Jitter measures the difference in measurements of successive ping tests.

A higher ping = higher latency, higher latency causes lag. Anything below 100ms may be considered acceptable for gaming. (Although some console and PC games can compensate higher ping values.) Zero jitter means each packet was received in the same amount of time. Within the Internet a small amount of jitter exists, and is normal. (Usually a fraction of the ping value.)

Line quality, and noise, can have an effect on all three of these. Ping can also be affected by the distance to the server, distance to your ISP's data centres, and method of transmission between the server and client.

Bandwidth is another issue with gaming.

Bandwidth is the amount of data that can pass through a network interface over a given time. (usually a variation of bits per second, bps)
Certain games require their game-servers to push a certain amount of data to the client (your console or PC). If there's not enough bandwidth to push all packets through, some packets are dropped. While the client may be capable of compensating for this loss, it can cause an adverse experience during online game-play. Fortunately for you, all three of these technologies could deliver enough bandwidth.

While the connection is fast enough, the latency may be an issue. NBN appears to be Mobile Technology, which tends to have high ping. This would be bad for gaming. The other two methods have ping values depending on the distance to the central station. They should be relatively low, though. Unfortunately there isn't a way to know for sure before contracting service.