You should not use broodlords, go with patriarchs...
Here is why:
1-it costs 162 instead of 150
2-His stats line is a bit worst
3-You CANT cast more then one catalyst per psychic phase ( which sucks I know.. )
4-The bonus +1
WS doesnt apply to putr genestealers cauz they dont have the <hive fleet>
5-Gargoyles suck in any situation, even if you cast onslaught.. dont waste time with them ( trust me )
6-Play pure
GsC unless you add exocrines and malanthropes, nids codex is bad...
( Whatever people think, imperium is way more versatile, units cost less, they carry good flyers, their characters are great, they have primaris and a wild pool of units... While we stand there with overpriced
HQs, poor firepower, can't deal with flyers spam, few combos, etc. The exocrines really shine but the earthshakers with battery is just so much better
lol )
7-If you play pure
GsC, think about adding primus, the re-roll on cult ambush's table is GREAT. Moreover, he gives you the same bonus as the patriarch.. Usually, you play 3 squads of 20 genestealers with 2 magus and a patriarch. This way, you can re-roll 2 tables thanks to primus and you can use a command point to re-roll it for the squad of the patriach if needed
Good luck mate !