The foundation chain is made of repeats of 4 + 5 chains.
You alternate a row of bobbles with a row made with sc and ch-2 spaces. You change colour for each row and each row is worked on the same side RS.
Gauge/tension it`s not relevant. Remember to leave long tails, at both start and end, for each row.

If possible, use what you have, dont buy more yarn! Any aran weight will do! In specific : my blanket weighs around 1300g and measures 110cm in width x 100cm in height, I think its a good size for a baby blanket!