Or you could pull a hypixel, and teleport players to a room, drop potion effects, and items from a dispenser, for a sec, onto a pressure plate, that has a delay onto the next TP. Adds a cool little transition, in which you can add multiple effects quickly and easily

Edit: oops, late answer oh well, I pronounce this thread dead from the neck up

Try adding a delay (repeater) to the teleporting command block, so you have time to pick up the items before you teleport.

I have it as

/give @p [item number] [how many]

It used to work like everytime I clicked the button it would give the items then teleport me somewhere else.

Now

I click the button, it summons the items, but the items drop and I get teleported to somewhere else.

Here's how it should look:
/give <player_name> <item_data_value> [amount] [damage_value]
<> are mandatory
[] are optional
if you dont specify a player name, use:
@p nearest player
@r random player
@a all players
@f farthest player (i believe; it isn't listed anywhere in mc, i saw it somewhere b4)

More info?