The budget allows you to increase or decrease the effectiveness of your services at rip-off prices. Decreasing your budget by 50% will actually decrease the output by 75%, and increasing your budget by 50% only increases your output by 25%.

For power and water, I see no reason to increase the budget past 100%, it's simply easier and cheaper to build new buildings.

For services such as school or fire, I like to crank those up to 150% once money becomes no issue. This is because their effectiveness goes up while reducing how many of those buildings I need to cram into each area.

Offices will satisfy your need for industrial zones within your city. However, this comes with a few important caveats.

Disadvantages of Offices

• Tax Revenue - Offices will generate lower tax revenue than industrial zones. As such, it will be harder to maintain a profitable city. Not hard, per se, just harder than if you zoned with industry.
• Job Creation - Offices do not make as many jobs available to your citizens as general industry, which means you'll need more offices to satisfy the same job demand. In addition, offices need educated citizens to staff them, so your uneducated citizens will be left jobless.
• Traffic & Goods Transportation - Goods can come from outside of the city via highways and any mass transit that connects to the outside world and has a cargo station. When your city only has office industry, the increased traffic tends to be more elevated and you'll need more transportation infrastructure to support it.

Benefits of Offices

• Provides Educated Jobs - If you're generating an educated populace, office work will make your citizens happy.
• Noise/Ground Pollution - Offices do not generate pollution of any kind.
• Lower Commute Times - Since offices do not generate pollution, you can place them right beside residential areas without ill effect. This can reduce the transit time for people to get to their jobs.