A popular strategy is to use vertically integrated industries where one industry produces the input of the next industry.
Energy and Water Edit
One of the important things to understand is that virtually every sector requires energy to run. It is the one inescapable resource, and expense, in the game. In the beginning, you can build Solar Power Plants without additional Research. You can also build Water Wells to start. Water is used in all mining, a couple of the more advanced power plants, smelting and a couple of other products. Many players advocate starting out with solar power and water.
The initial play would be to build the Solar Plant and let it run a while. The advantage is that no other input is needed. Just let it run and sell the energy, save cash, and build a second one. The disadvantage is that they are expensive to build and will not Produce a ton of energy. If you follow up the power plant with a relatively inexpensive Water Well, you will not need to buy power on the market to maintain the well. Wells produce fair amounts of water per hour (2400) that you can sell at just about any price profitably. Save the cash and build more wells while also building up your XP. Don't forget to vote and take your daily gift. The cash will help keep you building new wells. The solar power means that you will always get production from at least one well, regardless of circumstances.
You will only be focused on these buildings for a couple of days before branching into other things. The cost of power plants makes them hard to build quickly. Regardless, you will always be buying at least some power in the beginning, even with the plants. But a number of wells means a large quantity of water units for the market.
Wood and Sledges Edit
The other quick start is Sledge Workshops and Sawmills. Believe it or not, building them in reverse is not a bad idea, either. Sledge Workshops require only wood, which is a cheap commodity. They are one of the very few buildings that require no energy what so ever. Wood is inexpensive to purchase off the market. This makes the sledge an excellent product to make early. The workshop is very inexpensive to build, meaning that you can construct a number of them with your startup capital. Its a good thing, too, as they don't produce a lot of product per hour. A mere 420 units to be exact. Compare that to 1080 energy from a solar plant, or 2400 of a well. But they are so inexpensive to build, that you can make that distance up rather quickly.
After building a few workshops, build a Sawmill. Sawmills are also inexpensive to build. They do, however, require energy to run. The upside is that they produce a solid 5400 units an hour that sells profitably on the market. A single sawmill will supply all the wood you need for several workshops. The only downside is the need to keep energy available to keep them running. A couple days of steadily building these two facilities, and you will have a nice cash flow to work with as you develop.
Merging and Cleanup Edit
Whichever of the above you start your first days with, you will eventually merge them. Especially water, wood and sledges. You will be buying power, but you will also be making a steady profit. Build more of these facilities as your cash allows. Take your gifts and vote. That extra $125,000 a day is very helpful. But you will notice a problem, too. Trash.
Building a Waste Plant, and a Sewage Treatment Plant are generally considered the next step to laying a solid foundation to your budding enterprise. You don't want to be paying to have the trash hauled regularly, or any of the filthy waste water you will start accumulating soon. But, you can "buy" trash and waste water off the market, and get paid, instead of paying out, to get it. (It registers as a negative payout, meaning you see a gain to your cash, not a deficit.) Trash is turned into small amounts of steel, along with small amounts of waste water. Waste water is turned into clean water, and a bit of trash that goes right back into your waste plants. Both of the "clean" products can be sold on the market. It should be noted that the Sewage Plant needs some amount of Chemicals which you will have to buy off the market. It isn't a lot, so don't worry about it. Just buy it and keep moving.
Roll Your Own Edit
The last strategy we will look at is Pipes. It requires level 3 research and a broader investment in resources to build pipes. But, the lower number of units, viewed against the higher price of your finished product, makes this a viable enterprise. The Energy requirements are also minimal. The biggest expense here becomes Steel and Aluminum. Pipes require more varied inputs than other starting industries, making them a bit more complicated to manage, so perhaps not the best starting industry for a pure beginner. Many of the more experienced players do like it, however.
All of the above starting strategies will get you through the early days of a round in a solid form. You should have several of each building in your strategy after the first week, and have an established cash flow that will allow you to plan and execute your next steps. Which is good, because you are going to need it.