Drain chickpeas and rinse well. Cut cucumber into thin slices, then halve them. Cut tomato into wedges, then halve them. Put cucumbers and tomato pieces, as well as red peppers and scallions, in a bowl. Set aside. Dice avocado. Put in a large bowl, and add oil and juice from half the lemon. Add the salt, pepper and basil. Stir with fork (avocado will cream). Add the vegetables and dill to avocado mixture. Toss gently. Add chickpeas, and combine. Taste and add more lemon, salt and pepper as needed. Serve. Can be prepared ahead of time and refrigerated.