Purchase the largest cage that your budget and space will allow. Safety is of the utmost importance when purchasing a cage. Think of how much time your bird will be spending in his cage. Bar spacing, or any other gaps that are too close together can catch toes and beaks causing injuries. Likewise, with spacing that is too far apart.
Scroll work is attractive but can pose a safety hazard.
Be sure to check for sharp edges and doors that are not easily opened, to prevent accidental escapes. The addition of several toys will not only help keep these active guys busy but help keep beaks in good condition. Lovebirds' beaks are made of keratin which grows continuously, just like human finger nails. Chewing and destroying wood toys and perches helps keep beaks trim. Natural perches of varying thicknesses placed at different levels in the cage will allow greater climbing mobility and gives them a choice to select the most comfortable spot to roost.