Help with first robot project

I’m looking to build my first robot. I wanted to build a simple bot to sweep my table top without knocking over things on the table and without falling off of the table. I was thinking of having 3 small tires linearly arranged attached to a high torque relatively slow moving servo and a small brush or broom extending out from there.
Any suggestions on how to go about building something like this? are there kits that could make this project simpler to acheive? what sensors and controllers would work best here?

To confirm, you are looking for a robot to sweep dust and small items, but leave the larger items untouched?
Would you prefer to make it from scratch, or would a small robot vacuum do the trick?
Note that more intelligent robot vacuums have a variety of sensors so they don’t attempt to move larger objects and instead work around them, and others which prevent them from falling off stairs (or in this case a table)
If this is not what you want, can you perhaps clarify a bit more?

Yes i would like the robot to sweep objects like you mentioned but there wont be large items on the table to avoid. The table is in essence a table like structure with a slightly irregular surface and the robot needs to sense the tables edge which can be very curved so the robot would need to sense inclines and declines so that it can avoid going up the inclines/declines of more than 30 degrees.

Additionally i would like the robot to follow a non random path. I want it to start at the right upper corner of the table each time (can be any corner) and move down the table length wise not falling off the edge when it gets to the bottom or the side of the table. once at the bottom of the table it would move a few centimeters laterally and either turn around and go back up to the top of the table and stop. this process would repeat until it got to the other side of the table.

The robot would have to be heavy and slow moving with a lot of torque to be able to put some pressure on the surface it is riding on.

Because of all of these requirements im thinking maybe Boe-Bot but im not sure if that will do the trick and also if i can easily learn to do the programming to achieve what im looking for.

Can you provide an image or two of the surface? What objects will it be sweeping?
Some more information about the application will be beneficial (instead of having us guess).