I have a fairly extensive general overview of the Genestealer Cults faction
here if you would like to take a looksee.
At 1000 points you are going to be a bit limited, as many of the heavy hitting squads can easily exceed 250 points fully loaded and as a general rule of thumb (or claw) the army prefers redundancy to compensate for its fragility and to force hard decisions on your opponent. If you are just starting I'd probably look towards the newly released Tooth and Claw box as a starting point since everything within is useful for the cults (build Acolytes instead of Metamorphs). After that you will want to get your hands on some Neophytes to provide cheap bodies and fire support for your army and the other
HQ options as each has their own role to play and are all decent (Patrarch) to excellent (Magus/Primus). The Battleforce has both along with some additional Acolytes/Metamorphs and a Goliath Truck/Rockgrinder if you ever decided to give mechanized play a try.
When constructing an army the general principle you will want to follow is to have two halves: Your on-table presence (generally vehicles or cheaper infantry like Neophytes) and the ambushers (generally a Primus + melee payload). What army is your boyfriend looking to run?