* Chan eil e dona: This translates literally to "It's not bad," and is probably the closest direct translation. It's a neutral statement.
* Gu leòr: This means "enough" or "sufficient," and could be used to imply "it's good enough" or "it'll do." This conveys a slightly less enthusiastic approval than "Not bad."
* Math gu leòr: This combines "math" (good) with "gu leòr" (enough), resulting in "good enough." Similar to the previous option, but slightly more positive.
* Àrd-inbhe: This means "high-quality," "high standard" and might be used if the thing in question wasn't perfect, but above average.
The best choice depends on what you're describing and the level of positivity you want to express. If you provide more context (e.g., "Not bad for a first attempt"), I can give you a more precise translation.