Hey there! Exciting to see you taking interest in dart frogs! I would recommend D. Tinctorius! There are many morphs of different colors and are not as loud as other common beginner dart frogs. This species is very bold and active.. also very hardy making for a great beginners frogs. Although, this frog may be one of the largest dart frogs they really are not that big. No more than a couple of inches. I found a link for you!
Tinctorius Care - The Kapok Tree
Check it out and let me know what you think!
Anymore questions? I would be glad to help!
Take care!