At this age I found our DD (she is at home all day) getting bored so easily we had to really mix things up.
1) To keep existing toys interesting and engaging we needed to rotate toys. putting things out of site for a few days made them way more attractive (and played longer with)when they reappeared. We found access to too many toys meant she just looked at them and none of them were too exciting to play with. about once a week (after she goes to bed) I literally rearrange her play area so she spends a good day just exploring it to keep things exciting. I also found that setting things up in zones made her curious to go play in an area for longer rather than just having all her stuff in the center family room. This week I moved the coffee table behind the couch and she spent all day coloring at it because it was different. Go figure!
2) Some good outdoor or physical activity (even just a walk or ride-on toy down the block)in the morning seems to make for a much easier day (longer nap+more agreeable) and i get more done in the afternoon when i have to plow through chores.
Totally cliche but we love a good cardboard box (or laundry basket). DD would pile her stuffed animals, toys, books, treasures, push around the house, climb in, etc. I also got some bounce house balls in target and filled a larger box with those.
We also had fun with water. Sitting in a high chair I gave her a few cups of different sizes (measuring cup, plastic drinking cup, plastic utensils etc) put some water in a squeeze sports bottle and let her have at it.
Ride on toys are great (plenty of second hand ones out there) too. We got a toy baby stroller to push that keeps her busy for a few hours a week.
also filing and dumping activites seemed to be very fascinating at this age. a bucket of blocks can be fun to dump, fill, stack. We love her and my shoe boxes. You can use a few shoe boxes for things to fill and stack too. We have photos that we stuck on the front of shoe boxes for each family member and hunt around the house for something of theirs to put in the shoe box. For example As i move from room to room doing things she moves boxes around and helps find something to put in there (Daddy's sock, Mommy's barrette etc). great teaching, color, textures, who's box is heavier, who's is full or empty, what belongs in rooms of the house etc. It is silly but this sometimes is an all day activity (bonus for Mommy!).
Hope this helps!