There are so so many flight to Phnom Penh.
From air port to downtown, it cost USD12 by taxi.
For tuk tuk, it cost USD10 or so. Sometimes, tuk tuk is faster than taxi when heavy traffic jam.
Also bus from Bangkok and Hochi minh is available.
About hotel, it totally depend on location and quality.
Generally USD30 per day- or higher for standard/general hotel with air condition and shower.
For Guest house with USD5 per day. no shower.
For hotel with Casino, Naga World is only one and famous.