"越 ... 越..." (yuè... yuè...) is used frequently in Chinese to express that some quality or state is increasing with time, or in tune with another factor. There are two forms of this pattern, the "simple" one (using 来), and the more complex one (which uses two different adjectives/verbs) in Chinese grammar.

Basic Structure with 越来越
This structure expresses that something is becoming more and more adjective over time, with the latter adjective changing with the verb. The most common structure is:

Examples

Qì yóu yuè lái yuè ɡuì.
汽油 越 来 越 贵。
Gasoline is getting more and more expensive.

Complex Structure with 越 ... 越 ...
This structure can be expanded further by replacing 来 with another verb. This expresses that one change causes another change. To be exact, there are four structures to use. (The examples make it clear how this works.)
Structure 1
Examples

Tiǎo zhàn yuè dà, wǒ yuè xīnɡ fèn.
挑战 越 大，我 越 兴奋。
The bigger the challenge is, the more excited I am.

Structure 2

Examples

Tā yuè bù ɡāo xìnɡ, jiù yuè bù shuō huà.
她 越 不高兴，就 越 不说话。
The more upset , the less she talks.

Structure 3
Examples

Wǒ yuè xué xí zhōnɡ wén, yuè jué dé zhōnɡ wén hěn nán.
我 越 学习 中文，越 觉得 中文 很 难。
The more I study Chinese, the more difficult I think it is.

Structure 4

Tā yuè hē tàn suān yǐn liào yuè pànɡ.
他 越 喝 碳酸饮料 越 胖。
The more he drinks soda, the fatter he gets.

Complex Structure with Complement

You can also use "越...越..." with a complement. In this case, "越" has to follow the "得". This construction usually uses "State complements" and "Result complements".

Examples

Nǐ mǎi dé yuè duō yuè pián yi.
你 买 得 越 多 越 便宜。
The more you buy, the cheaper it gets.