If you already have the system & have a limited budget, then you might as well see what you can upgrade on it.
From the owner's manual (http://downloads.dell.com/manuals/all-products/esuprt_desktop/esuprt_vostro_desktop/vostro-260_owner%27s%20manual_en-us.pdf), the 260 has a 300W PSU, & the 260S has a 250W PSU. Neither is going to be great, but they should be able to handle lower-power GPUs (i.e. ones that don't require PCIe power connectors). I would stick more with a GTX 1050 instead of the 1050TI,because a) it'll be a lot cheaper, b) the 1050TI is more powerful but not decidedly so for its cost, & c) it's a lot easier to find GTX 1050 cards that don't need PCIe power connectors. If you have the 260S with the lower PSU, you could...