Reducing the size of the training data

Question

My problem is that running Classify on my training data takes too long.

First I get 50,000 images such as car, cat, dog, hat, train, etc.

data = ResourceObject["CIFAR-100"];
ts = ResourceData[data, "TrainingData"];

Then I try

Classify[ts]

but it takes too long.

I probably need to preprocess the training data test set to reduce its size before calling Classify. What is good way to do that?