hot air balloon centerpiece made with regular helium-filled balloon, mesh net, wicker basket weighed down with marbles or rocks.<------ I've done these. Not with helium balloons but with regular ones. Not too hard and super cute.
“Centerpieces add up. When deciding on your reception centerpieces, not every table needs a lavish floral arrangement. Candles are a good way to save money. Alternating non-floral centerpieces like floating candles, a cluster of pillar candles in varying heights, mason jars, wine bottles, or fruit arrangements creates an elegant and modern look.”