First off, it's gh, or giga hashes, not giga herz.
You have multiple choices , just make sure the prices and ROI is realistic, and not some too good to be true ponzi. I used to have mining power from ghash.io,
but recently it seams that bit-x is also a legit company.
You could also rent out rigs from individual users on services such as leaserig and betarigs.
just be sure to keep in mind that if you are renting a rig for x amount of time, you will be losing out, 100% of the time. there is absolutely zero reason for someone to rent their rig to you if they would be making more mining themselves in the meantime; they are making a profit by renting hashing power to you.
