We study the formation, evolution and clustering of galaxies in standard and modified gravity universes and prepare synthetic catalogues for future galaxy surveys, such as DESI. To do this, we have run and analysed N-body and hydrodynamical simulations of different gravity models. In the first part, we focus our attention on two of the most representative and popular families of modified gravity models: the Hu & Sawicki f(R) gravity and the normal-branch Dvali-Gabadadze-Porrati (nDGP) braneworld model. We use mock galaxy catalogues constructed from a halo occupation distribution (HOD) prescription with the HOD parameters in the modified gravity models tuned to match with the number density and the real-space clustering of BOSS-CMASS galaxies to analyse the marked correlation function in three variants of the f(R) gravity model and to measure galaxy clustering in redshift space in both f(R) and nDGP models. In addition, we introduce the first set of full-hydrodynamical simulations of galaxy formation in the nDGP model using a new modified version of the AREPO code and the IllustrisTNG galaxy formation model. In the second half, we explore if there is an optimal way to select a galaxy sample in order to measure the baryon acoustic oscillation (BAO) scale, which is used as a standard ruler to constrain the cosmic expansion. Also, we present a covariance and clustering analysis of DESI-like luminous red galaxies (LRGs). For the latter, the mock catalogues are built with a novel technique using the semi-analytical model of galaxy formation GALFORM and a large number of halo catalogues generated using the Parallel-PM N-body GLAM code
