I’m going to go against the flow here: I would advise against a poodle or -doodle. I would also be wary of most terriers. Here’s why:
When you say “easy to train”, what do you really mean? Do you want or need a dog who is very attentive and listens well, or are you looking for a laid-back companion who’s happy and relaxed? For the sake of this question, let’s assume you cannot have both – I think I remember you asked a question about that a long time ago.
Here it is.
In my experience, the smart dogs – attentive ones who were bred as hunters or herders – can make very difficult pets. Poodles are whip-smart and extremely trainable, but that attentiveness comes at a price – lots of them turn out to be nervous, even fearful. Terriers were bred to be independent hunters, and their energy level and curiosity makes them fun to be around. However, that same energy level is a lot to handle in daily life, and when you don’t keep them sufficiently amused they will find their own entertainment.
If it has to be a small dog, I would recommend a pug or French Bulldog, but one that is bred to be like the original version – none of the crazy short snouts. Alternatively, if you can vow to spend ten minutes a day on whistle training for the first year of your puppy’s life, Beagles make amazing cuddle companions and are usually very friendly and extremely chill. There’s a reason why they are the most common laboratory dogs. Beagles are hunters too, of course (hence the whistle training), but they are much less independent.
That said, there is a lot of variation within breeds and I am just talking statistics here. You might get lucky with any dog, and even the perfect puppy can be completely ruined by a careless or clueless breeder.