I want to write the words "God's blessing" in Latin. I came up with the translation Deo donante after a Google search. I want to double check if Deo donante means "God's blessing" and to understand what it means. What is the meaning of donante?
"God's blessing" in Latin is benedictio Dei.
This phrase appears in the last sentence of the Pope's Blessing to the City and to the World (Urbi et Orbi):
Et benedictio Dei omnipotentis, Patris, et Filii, et Spiritus Sancti, descendat super vos et maneat semper.
And may the blessing of almighty God, the Father, the Son, and the Holy Spirit come down on you and remain with you always.
It's not a distinctively Catholic phrase, though. Latin is an international language, and the early Protestants used this same phrase. Here is some discussion of John Calvin's belief that life is a benedictio Dei.
Deo donante literally means "with God giving", though it could also mean "while giving to God". In English, the -ing form of a verb serves as both present participle, i.e. as an adjective, as in "The man now surfing is the defending champion", and as gerund, i.e. as a noun, as in "The surfing today is wonderful." In Latin, the present participle and gerund have distinct endings. Donante is a present participle, not a gerund, so it's probably not appropriate for what you have in mind, as it sounds like you want a noun to denote God's blessing, not a modifier for something else. It's also in the ablative case, which provides a wonderfully concise way to express some kinds of thoughts, but it might not suit what you have in mind. See my explanation of the related phrase Deo iuvante here for more detail.
Corresponding words in different languages often have a slight difference in meaning or connotation. So here's a little more information to give you a little of the "feel" of benedictio in Latin. Benedictio is a compound word: bene means "well", the root of English words like "benevolent" and "beneficial"; and dictio means "a saying, talk, oratory", whence English "dictionary". The English word "benediction" is of course a direct borrowing of Latin benedictio. Here's an example of its usage in St. Jerome's translation of Genesis 26:28–29:
Qui responderunt "Vidimus tecum esse Dominum et idcirco nunc diximus sit iuramentum inter nos et ineamus foedus ut non facias nobis quicquam mali sicut et nos nihil tuorum adtigimus nec fecimus quod te laederet sed cum pace dimisimus auctum benedictione Domini."
They responded, "We saw that thou art with the Lord and for that reason we then said, 'Let there be an oath between us, and let us enter into a covenant that thou do us no harm just as we have touched nothing of thine nor have we done anything that would harm thee; but with peace we sent thee away enriched with the blessing of the Lord.'"
Translation mine, written to make the parallels between the Latin and English as easy to follow as possible.
Benedictione is the ablative of benedictio, indicating its connection with auctum (enriched).
Deo donante is not a good translation. It is an absolute ablative and has numerous meanings. Depending on context, it can mean "while/when/because/if God gives", and there is no single universal translation.
Deo donante plays a very different grammatical role than "God's blessing". The English phrase is essentially a noun, whereas the Latin one is essentially a subordinate clause. This is not technically precise, but I just wanted to point out the difference in nature.
The genitive "God's" is best translated as the Latin genitive Dei. The main problem in translating "God's blessing" is finding a good word for "blessing". You can look up any noun you like in any online Latin dictionary and use it as such. I agree with Ben Kovitz that the most appropriate word seems to be benedictio. Therefore benedictio Dei is my suggestion.
There are many horrible Latin translations out there, and Google Translate excels at producing more, so it is wise to consult someone who understands Latin in matters of any importance. I would of course suggest this site. ☺